That's not plausible at all. Robert Wadlow as at the very limits of human height. He already numerous medical problems caused by his height and needed leg braces just to walk.
There is no way a bronze age man with access to bronze age medical care was able to live long enough to grow nearly 3 feet taller than Wadlow.
Since weight doesn't scale linearly with height, a 12' tall man would be enormous. Robert wadlow weighed nearly 500 pounds. A 12' tall man would weigh much much more than that.
I think there are only 2 real possibilities to explain the giant. Either he wasn't really as tall as the discoverer thought, or something was different to allow him to get that tall.
On the latter point:
"There is no way a bronze age man with access to bronze age medical care was able to live long enough to grow nearly 3 feet taller than Wadlow."
You don't know that. Even in antiquity, with Iron Age medical care, men commonly lived to 100 years, with the absolute limit, as placed by the Etruscans, at 110 years, thus defining the Etruscan century at this number. Now, perhaps if the man in question was a giant there would be intrinsic difficulties in being gigantic, but natural selection within his tall genetic group could, as a group, overcome many of them. This is a very different situation that Robert Wadlow's, who did not come from exceptionally tall parents. If a group has selective pressure to become tall, it's an entirely different matter from an individual accidentally becoming tall.
Keep in mind there have been around 60 billion Homo Sapiens Sapiens, most of them outside historical record, and in prehistory, very isolated. This can commonly lead to vast phenotype differences. I would have to see stronger evidence to rule out that an adapted giant biped cannot reach 15 feet.
I didn't say an adapted biped can't reach 15 feet, but a modern human with a pituitary tumor cannot. Which is what the OP suggested. There are too many health problems associated with 9' giants of Wadlow's type for bronze age medicine to overcome, much less 12' or 15' giants.
>You don't know that. Even in antiquity, with Iron Age medical care, men commonly lived to 100 years, with the absolute limit, as placed by the Etruscans, at 110 years
I'm not talking about the lifespan of a normal human who happens not to develop any terminal illnesses, I'm talking about the lifespan of a giant with a pituitary tumor. At the extremes they have too many medical problems to live anywhere near a normal lifespan. Wadlow could barely walk, he couldn't feel his legs so he constantly developed blisters (this is what eventually killed him by the way), and like all extreme giants he had heart problems because his heart was enlarged and couldn't handle his pumping blood throughout his enormous frame.
Keep in mind these are the problems with a 9' giant. Now imagine the medical problems of a 12' giant. He would be a third taller and probably at least 2 times heavier. There is no way someone like that is going to survive in the bronze age, unless he is either of a subspecies that is adapted to growing that tall, or conditions were somehow different.
Absolutely, yes - and, given that the normal lifespan has been three score and ten for about as far back as we can see, and given that Wadlow managed only one score and two, what're the odds that nobody with Wadlow's afflictions ever managed longer?
My point is, Wadlow's death was effectively a matter of poor luck - a blister popped up and went septic that he didn't notice soon enough, but others had previously been spotted and dealt with. Who's to say that no Iron Age 20 year old could possibly do better?
It wasn't a matter of luck, it was because of his condition that he couldn't feel his feet and thus developed blisters. It was just a matter of time until one of his blisters or other feet injuries got infected. And in the bronze age with no knowledge of germ theory, much less antibiotics, these infections would likely prove lethal.
Robert Wadlow wouldn't have lived very long in a tribe in ancient France with a condition that caused chronic blisters and foot wounds. Furthermore gigantism causes extremely high blood pressure leading to varicose ulcers in the legs and again, infection.
However, the blister alone wasn't what killed him, he had an autoimmune problem caused by his disorder that contributed to his death, and he had an enlarged heart and was generally unhealthy.
>Who's to say that no Iron Age 20 year old could possibly do better?
It's not do better, it's significantly better with vastly inferior medicine. Even if his growth rate remained at the rate it was during the last few years of his life he would have to have lived almost 20 more years to grow another 3 feet. In addition his growth rate most likely would have slowed or stopped eventually.
If he had continued growing the strain on his skeleton and circulatory system would have killed him way before he got to 12'. This kind of gigantism is a disorder that causes immense strain on the body, humans just aren't build to handle that level of growth hormone.
Have you noticed that there are only 3 people in all of recorded history who reached 8.5' tall. The reason is because that is basically the upper limit of what is survivable.
Even if it were possible for a 12' tall man to live, given a population 10 times larger (all the people who ever lived compared to all those born in the 20th century) what's the chance that this population produced a man 3 feet taller than the tallest in recorded history--Keeping in mind that people with this disorder would have been likely to die even earlier than the giants of the modern era due to the lack of any semblance of modern medicine.
But that's not remotely comparable to someone growing 3.5 meters tall. Nowadays there are also plenty of people who live more than 100 years, and not all of them need extensive medical care.
Growing to 3.5 m is more comparable to finding someone who lived to 200 years.