What you appear to have done is: spend 10 minutes reading the article, then 5 minutes complaining about how it is unreasonable to expect anybody to read 3,000 words. 15 minutes in total. (All times are estimates.)
Perhaps a better course of action would be: spend 10 minutes reading the article, and then wonder perhaps how you could put its advice into practise. 15 minutes in total.
Suppose you take its advice to heart and immediately end up being able to do what I did and read articles such as this one in 2 minutes. Your total time investment for reading n articles (excluding this one) will then be 15+2n. Maybe it takes longer to get the hang of, and it works out as 15+5n?
But suppose you continue as you are - time investment for the same will be more like 15+10n. A steeper graph. (And actually, more like 20+10n, because those 5 minutes you spent complaining are now spent.)
I think this is the guy's point.
(How do I spend the time I save? Why, by writing comments such as this, of course.)
That said, I would like to address your claim of a 2min. read-through:
"but I used my stopwatch and it took me pretty much exactly 2
minutes to read. I studied subjects at school that required a lot
of reading, and so I probably got the practice from that. (Of course,
not all texts are suitable for reading this way.)"
Speedreading is snakeoil. [1]
[1] http://lifehacker.com/the-truth-about-speed-reading-15425083...
Once you've got through 3,000 words in 2 minutes, you might not recall all of it, but you'll at least be able to tell whether it's worth going back for a closer look, or just making a mental note, or forgetting the entire experience.
This isn't a useful technique for everything. But when/if you have a huge pile of big, thick books to get through, all printed in small type with thin margins - probably the sort of thing the author here is thinking of - your options are a bit limited.