"a rule long ignored is now being enforced"
And therein lies the rub : consistency. Apple is well-known for wanting to control everything, but how it controls is not consistent. It is useless to lay down a rule if you only enforce it after years of ignoring it. That is how you get backlash and discontent among your user base.
Of course, it may be that Apple has decided it doesn't care, but the lapse between declaring the rule and enforcing it is just sloppiness. When a company decides to only accept Word files as job submissions, you can bet that it won't let the first 20 PDF files through anyway, just because. No, those PDF files are going straight to the round filing cabinet and those who submitted are likely never even going to hear about it.
Biting the hand that feeds IT
