I suggested that in other threads that iPP could optionally boot MacOS when docked. Would I use it much? Not likely as the touch interface would disappear. I rather see that MacOS apps was recompiled to work on docked iPads as these apps requires keyboard and trackpad.I agree with what you are saying except you need to acknowledge that having the best of both worlds would be possible with a dual boot iPad Pro. There would be no difference between an M1 MacBook Air and and 2021 iPad Pro booted into Big Sur with a magic keyboard except 1 thunderbolt port and an extra .3" of screen. none.
For me iMac/MP+iPP is a super combination and it has been so for years. With the easy ways to share a keyboard/trackpad, we are really getting somewhere.
Could we also get the devices to automatically form a compute cluster when connected over thunderbolt? It could be very useful for renders or similar jobs.
For home use, I only use iPad.