Oh, lots of stuff gets invented multiple times, when it's "in the air". Nothing special about Chomsky here. And I wouldn't see that distracting from this particular achievement.

I'm a big Chomsky nerd, Chomsky fan, and card-carrying ex Chomskyan linguist. I hate to break it to you, but not even Chomsky thought that the Chomsky hierarchy had any very interesting application to natural languages. Amongst linguists who (unlike Chomsky) are still interested in formal language classes, the general consensus these days is that the relevant class is one of the so-called 'mildly context sensitive' ones (see e.g. https://www.kornai.com/MatLing/mcsfin.pdf for an overview).

(I suppose I have to state for the record that Chomsky's ties to Epstein are indefensible and that I'm not a fan of his on a personal level.)

Lots of things get invented / discovered multiple times when it's in the air. But just because Newton (or Leibnitz) existed, doesn't mean Leibnitz (or Newton) were any less visionary.

For your very specific question: have a look at the sorry state of what's called 'regular expressions' many programming languages and libraries to see what programmers left loose can do. (Most of these 'regular expressions' add things like back-references etc that make matching their franken-'xpressions take exponential time in the worst case; but they neglect to put in stuff like intersection or complement of expressions, which are matchable in linear time.