Regarding M-mount lenses on FE... It’s really a case by case basis. It comes back to expectation management and a lot of people have spent countless hours on modifications and workarounds if they intend to use the FE cameras exclusively with M-mount lenses. Focal length alone isn’t the lone determination and there are native alternatives now that offer in built correction and the ability to focus at a closer distance if you choose to get the Zeiss Loxia or Voigtlander variants of the lenses. Again this is a old argument that yes, non-native lenses can possibly come with undesirable side effects but the people that chose the SLR variants from say the Leica R didn’t deal with any of these issues. It was exclusive to SOME rangefinder lenses and mostly with the Leica branded aspherical lenses from my personal experience. Most of my Voigtlander and Zeiss M mount lenses worked flawlessly without issue but I eventually bought native alternatives that added functionality like AF and closer focusing once the system was built out. The Sony FE lenses were ahead of their time in many ways and sort of set the tone for modern mirrorless AF lenses that are great at BOTH photo and video usage. No one other than really Panasonic was developing native lenses that had both in mind and it showed. Adapting (IMO) is mostly a stop gap for me or a thing to do for a specific look to the imagery.Absolutely your right to argue about these facts - but it does not change anything about the physics of the mount and how much freedom you get to design great glass with great IQ and maybe less effort if you have mounts like Z or RF compared to FE.
I think everybody is aware about the issues of the Leica M mount which was designed for film around 60 years ago and only since 10 years Leica found a way to use digital sensors inside a digital M and make the M mount finally digital. It has all to do with the need/lack of tele centric lens design for achieving superior quality and/or the need to use special micro lens design at the corners of the M sensors in combination with pretty thin glass layers in front of the sensor.
BTW my M lenses (even WA) work almost perfect on my Z7 with a standard M to Z adapter, while this cannot be said for using M lenses on the FE mount - another criteria for me to not go Sony FE.
But I do not want to get further into boring comparisons and argumentations - from a technical point of view Nikon Z and Canon RF deliver a far superior platform for the design of exceptional lenses compared to smaller mount diameters and larger flange distances. This is simply a given and not debatable. If it really finally matters WRT IQ etc. remains to be determined by the end users who decides to buy into one of these mounts.
For me at least these differences (and upcoming possibilities) mattered and hence there remained 2 systems/mounts - Z and RF - and I finally happened to chose Z because of ability to get a good price for the overall package - it is/was as easy
Now I will agree that the Nikon Z is a better platform for M lenses than the FE bodies in general but that has nothing to do with mount size alone. It’s likely a combination of the sensor stack, distance to sensor, mount size, etc. The SL/SL2 are far better cameras for adapting M lenses and it has a smaller mount than the Z or RF. It also includes software corrections. The M is the best platform to use M lenses and it has a mount smaller than all of the cameras mentioned.
I think everyone is talking in circles at this point though. I really only responded to clear much of the air. Everyone has different desires/needs and that pretty much sums it all up.