So, the FM2 was 0.86x magnification, pretty close to the 0.9x of the Olympus OM-1. That explains why I liked the FM2 as well.
In addition to facial structure and eyepoint, subtleties of the glass prescription, curvature and thickness of the glass could determine, if a viewfinder works for an individual or not.
I once had glasses for use with contact lenses and another pair with another prescription for use without contact lenses. Suffice to say that they didn't work equally with the same viewfinder. So, the prescription matters as well.
Luckily, EVFs works well for me.