In this consideration, we need to keep in mind that mechanical wear and tear is not entirely confined to the mirror box and mechanical shutter...switches develop faulty actuations (dead, intermittent or noisy) just by being pressed/rotated, or sometimes even from insufficient frequency of actuation!
And electronics can stop functioning, too...
- the reason why some folks have recently inquired about why their flash units have not been operating (not an issue with a switch, nor with electrical contact in the hot foot)
- I have a Canon 5D (classic) that simply stopped functioning in the middle of a shoot ...after I put it down on the table to do something (without switching it off) and picked it up again, it would not wake up for continued use! Circuit malfunction in a camera with less than 60K actuations.
The mechanical shutter count was a means of determining just how much a camera had been used to take exposures. Yet that would not factor in a lot of handling with zero exposures taken. Yet that is how many cameras are used...point and focus and decide not to shoot, for whatever reason. So even shutter count has its shorcomings in determining 'wear'.
And my 7DII has only less than 50k actuations, yet it has very flakey main rotaty switch intermittent contact, that seems to be progressively getting worse over time and is the greatest frustration to continued use of that camera...definitely not a case of overuse, and spinning that dial does not seem to be cleaning contacts that might have gotten oxidized so not a case of underuse either!
So electronic shutters add a bit more undertainty into a very inexact measure of 'wear'.