The relative resolutions of APS-C and FF do, of course, depend on their number of Mpx. But, even comparing the 45 Mpx R5 and the 32 Mpx R7, there is still a fov advantage to the R5 at the same resolution. For example, a shorter 370mm lens on an R7 gives the same number of pixels per duck as a 500mm lens on an R5. But, the field of view of 370mm on the R7 is that of a 590mm on the R5, giving the R5 a non-negligible 18% advantage in fov.
The odds are that Canon will come out with an FF of about 88 Mpx, the same pixel density of the R7, just like they did for the 5DS vs 7DII, and we will then be back to the 60% fov advantage of the FF vs APS-C.