Much ado about nothing.
You will also find MLU invaluable when using the TS-E 24mm F3.5L (I or II)!
Cf 12 1 or 0 accomplishes MLU activation or deactivation. It's usefulness is doubled with 2 or 10sec self timer for remote photography or when commencing an invervalometric process like star trails. There is no sweat to on any of the Canons — it is that you have not warmed to idiosyncracies with Canon. All cameras have their own personalities. I've been using the 1N since 1996 and know all of the custom functions to memory.

If you want it "up front and there to see", try the ginormous SLR-on-steroids Pentax 67 body with MLU. A tiny slider right side front mirror box engages with a gentle toot and the mirror's up (albeit draining the battery while you are procrastinating about a change in the scene before you...). With this beast, you need all the vibration dampening on offer, then some.