Absolutely, the L RF lens outresolve R5 sensor, I believe this is well established. The argument that this is a reason for keeping the 1 series sensor definition does not hold water.
The fundamentals of resolution are simple are simple, frankly, as long as you only consider resolution. Sensor should always be outresolving the lens, because you don't want the other way around and loose info. One is limited by the lens they carry, that lens has a max resolution (in the center likely), so you want the sensor to get the max details so it needs out outresolve the peak (center) definition. Simply because you would want to extra all the definition from the lens you carry around, not loose some.
The many problem problems with high definition sensor (manufacturing defects/cost, speed, heat, storage, etc etc ...) are the reason why a low MP is favored in some cases, mainly when speed or marketing is in sight. But resolution is a simple debate, out of context, capturing more is just better.
Personally I will go for the R5 mk2 over a lower-MP 1 series. I made the same choice going for 5D4 instead of 1DX2, and while I regretted the fps drop (12>7fps) from my 1DX1 and not-as-confortable viewfinder, I really enjoy the 5D4 definition increase.
What I like most in those R1 images is a large EVF. With my glasses, a super large EVF would be lovely, I still find the R3 one too tiny for my taste.