I can understand those hardware limitations, but the real head scratcher is why remove 1080 24fps, limit EF-S lenses to 4K and 720(no 1080) and removal of most exposure modes from the video modes?
If the 4k DPAF is a hardware limitation (which I don't think based on their M50 interview) in that case, no EF-S 1080p can also be explained with hardware, it would be downsampled from the cropped 4k image (just like the EOS R), and that coupled with an IPB codec, is more processing intensive than just writing it in 4k and compressing that straight away. They don't have a separate line-skipped 1080p crop mode (why would they, get an M50, it would be much better than the RP for that, but 720p is also a waste of programming time)
Actually, apart from the A7S series in up to 1080p 30p, I think all Sony cameras have line-skipped 1080p video (which is also much weaker) they only downscale to 4k and not 1080p.
The EOS RP does still have a fast UHS-II SD interface, so it could certainly be hacked to provide more high-end video stuff, but a fairly new processor with the new CR3 Raw format, I really don't think it will go anywhere, while this is still relevant.
Compressed Raw option is actually very good here, but no M50 hack in sight to have anything from the past as a solid base.
There are some promises for the EOS R...we'll see I guess...