Indeed, except for possible upgrade path issues, they would be better of with APS-C M system and FF R system.
Only time will tell but my guess is that Canon might have been better off with an expanded M-mount line-up for APS-C and R-mount for top end Full Frame.
That's what Canon said they wanted, back in 2018. Unfortunately sales figures seem to have told them that they( and you and I) were wrong
Can you point me at any article where Canon said that.
I can't find it any more as I've replaced my phone twice since then and my computer once, but there was a Canon white paper in about September 2018 about the RF mount and any amount of marketing guff about how EOS M and EOS R were APS-C and full frame systems linked by EF lenses. I don't think Canon publish model by model sales figures but judging by the speed at which the EF lens range has contracted, with quite mainstream lenses being discontinued that have no RF equivalent (20mm/2.8, 100mm/2, 200mm/2.8, 300mm/4, 400mm/5.6, never mind all the ones that do have RF equivalents) suggests that EF sales are dropping off badly.
Also I think it's far too early to jump to any conclusion as RF-S is still relatively new. But if you have any sales figures that would be interesting.
Thanks.
RF-S is very new, but my gut feeling is that there's less room for fast and exciting RF-S lenses than for fast and exciting EF-M lenses. Not that I'd be interested in them anyway.