Why does the EOS RP apply a crop to an EF-S lens in photo mode, then apply ANOTHER 1.6 crop in 4k video? Please, Canon, allow us to choose NOT to crop EF-S lenses. We bought a camera with a full-frame sensor for a reason.
Sorry, but you are not making any sense. That is not how it works. Do you understand the difference between lenses made for the EF mount and those made for the EF-S mount? The Image Circles that the lenses project are different sizes.
The cropping with EF-S lenses is not done in firmware. It is merely a fact of how the lenses are built.
I may be mistaken, but I do not believe any cropping occurs in the EOS R when it records 4K [with and EF-S lens], and I believe the RP works the same way. You will actually get a wider angle of view at 4K using an EF-S lens than you would with an EF lens.
BTW, Canon makes professional cinema camera, which use Super 35 image sensors. There are just a little larger than the APS-C sensor used in Canon DSLRS. The cropped 4K produced by these cameras produces an angle of view that is very close to the angle of view captured with the same lens by Canon's 4K cinema cameras. I think it is just a coincidence, though.