Instead of pondering what you should and would do on an iPad, and what some unsubstantiated number of people actually do with their iPads, I think it would be better if Apple avoids promoting and highlighting a feature that isn't ready out of the box or has a list of caveats.ProRes will fill an iPad's limited storage space quickly, too. 99 out of 100 iPad users don't care and would be better off with hvec format video.
If this is a bug then quality control is out the window.
If its weird artificial limitation that actually requires you to use third-party apps then it's highly misleading to not point this out in the presentation or on the product page.
Any way, really dumb no matter how you look at it.