Jack, your thinking is what was behind my Reply #3 in this thread.
There are several lists of lens register distances on the internet; an up-to-date one is here:
https://briansmith.com/flange-focal-distance-guide/ Some groupings of Nikon and Leica register distances relevant to the discussions in this thread are:
Nikon Z 16mm, Nikon S (Rangefinder) 34.85mm, and Nikon F (SLR) 46.5mm.
Leica L 20mm, Leica M 27.80, Leica M39 Screw 28.80, and Leica R (SLR) 47.0mm.
Both rangefinder and mirror-less register distances are ~2 to ~3 times smaller than their SLR counterparts, hence imposing less constraints on lens designers.
In the instance of the Nikon Z mount, not only is the register distance the shortest in its class, its throat diameter is the largest, thereby reducing another design constraint. The Nikon Z lens designs have, I am sure, benefited from the reduction of these two constraints resulting from the design of the Nikon Z mount.
Whether the more perfect modern Z lens designs that have followed this new mount will exhibit such "Glows" is what I am wondering about. I think that there is more to this overall question than coatings alone.
To make short lenses work well on cameras with large register distances a retro focus design was often used. This can indeed change the character of the lens. Close range correction (CRC) was also employed with shorter lenses to allow them to perform well. They typically change the distance between lens elements to do this. This will also have an impact on the “look”. In lens design there are a number of different parameters to be juggled. Prioritization of one can have a negative impact on another, so choices need to be made either explicitly or by letting the chips fall where they may.
Mirrorless with a shorter register can make it possible to not use a retro focus design which can give a designer a bit more freedom.
