Why do you care?

It's his hobby/passion project, I really don't understand your objection.

You seem to have a problem with the fact he criticises other languages. Would you also treat someone who isn't currently designing a language with the same harshness if they also criticised a language the way Jonathan Blow does?

...Except that he did talk about all of his games almost from the get go? He showed earliest prototypes of Braid and Witness publicaly when the games were just blocky protypes, in the latter case good 7 years before the game came out. I don't know where you got this idea from, the way he is handling the development of the language seems to be pretty much an extension of how he develops his games.

C was largely "finished" when it came out–future additions have not added much. And by "finished" I don't mean "never changes", I mean "finished enough for a 1.0".