I bet there is no technical hinder to port any full app to iPad OS. The obstacle is if the market will adapt it and if the AYYX processor is powerful enough. Considering the OTOY made a ray tracer for Mac and iPad (!) things are changing. I had to read it twice that they put ray tracing of 3D models on iPad. I expected that was the last application that would reach iPad due to the weak power of AYYX chips compared to GPUs.
YES! EXACTLY!
It's not a technical limitation but rather a resource problem. Unless your audience is primarily mobile, if you have limited resources you're probably going to build a desktop app (especially if you already have one).
I think the debate of a Desktop OS vs. a Mobile OS is still siding with Apple's split method... for now. For me (in my opinion only) Windows 10 is still not very friendly for day-to-day uses like the iPad. Windows 10x may change that, especially with the Surface Neo and Duo.
I recently bought a Surface Pro 7 (not to replace anything - still use my iPad more than anything else), and I'm VERY disappointed by the battery life. Even trying to do things like take notes in OneNote drain the battery WAY too quickly - I get 2, maybe 3 hours (and Microsoft has been no help). I could never trust the Surface Pro 7 for a day's work with no charging like I can trust my iPad. Kind of disappointing.