> it's not a secret how metamphetamine is made
I didn't say it was a secret. But try sharing the recipe to methamphetamine virtually anywhere online and see how long it stays up; we do in fact try to at least make it moderately difficult to find this information. Perfect is the enemy of good here.
> No one - I believe - knows how to build an AGI.
The problem is that if we wait until someone does know how to build an AGI, then the game is up. We do not know if the weights behind GPT-4 will be a critical ingredient. If you make the ingredients common knowledge before you know they were in fact The Ingredients, you've let the cat out of the bag and there's no retrieving it.