Why is it "concerning"? Personally, I get a lot of stuff done on the $200/month subs. +$100/day per employee seems like a fairly significant amount of money and if a lot of companies do that (even a lot less than that) that seems entirely fine for frontier labs, given all the other uses as well.

That is not to say that you can't spend a lot more. And I would be surprised if Apple did not allow for that too. Note that the text says "for some of its own engineers", which could amount to a total nothing-burger, given the overall vagueness.