Not really. It’s a condition. You can also choose the old rules.. you can also chose to not develop for iOS. There is no gun to your head if you don’t develop for iOS
Where is the line? Surely at some point, the choice is so unreasonable that Apple has effectively forced developers into "the old rules," thus circumventing compliance with the new rules, which may as well not exist if no developers can afford to play within them...
I never write code for Windows and actively tell any client I have to not use it if they want my product. If they don't want it so much - there are plenty of alternative. If they really want it - they will use the OS I write the app for.