As you point out, 40ms delay doesn't matter for shutter timing. Coming at it from a gaming and controls perspective: delay can make it a little harder to track things, though. I don't know how big of a deal this is to real users. I do know that the sheer amount of blackout on almost all current mirrorless sucks.
> Once AF and motor drive happened, the technique shifted from trying to hit the decisive moment, to just mashing the shutter and picking the best shot from the series.
Yah, and this is a place mirrorless cameras win and even phone cameras perform very well-- 10 picture/second burst rate on iPhone which few DSLRs can match. Middle/lower end Canon now is hitting 15FPS mechanical shutter and 23FPS electronic/silent, which is absolutely nuts to me (I have memories of buying a "blindingly fast" 7FPS camera..)
The OVF lag on the high end models is significantly faster than the time it take the mirror to retract (a D5 SLR has about 40ms of shutter lag). This means that while you might have a very minimal lag on the EVF, you make up for it in shorter shutter lag.
Just a note: I used to do Photojournalism for a living. This kind of precision timing is irrelevant for action shooting. Once AF and motor drive happened, the technique shifted from trying to hit the decisive moment, to just mashing the shutter and picking the best shot from the series.