EOS R5 Mark II "Optical Viewfinder simulation assist" won't work if EVF brightness not set to "Auto"

[C-Cella]

The title says it all pretty much.

The manual doesn't clearely mention the limitation at all: https://cam.start.canon/en/C017/manual/html/UG-03_Shooting-1_0410.htmlI

There is a vague statement: Depending on setting screens, optical viewfinder simulation may not be used for display.

The main issue is that the option ceases to work even for the main screen.

If the user is looking at the main screen the options should work because the main screen brightness can be "custom".

iSo:

If main screen brightness is custom and EVF brightness is Auto then "OVF Assist" always works.

If main screen brightness is custom and EVFrightness IS NOT auto then "OVF Assist"option only works on screen. Warningiin EVF, maybe the option icon should be red as in error, this that case.

Manual andenu should mention at least this case (it took me like 15 minutes to understand why "OVF Assist" was not working anymore, it's not easy to discover)

[jrhoffman75]

On the R6 Mark II if viewfinder brightness is not set to Auto the option to select OVF Assist is greyed-out and if it is selected a message pops up saying can't be enabled because of current setting and says viewfinder brightness.

[C-Cella]

That appears in the "Assisted Shooting" menu but no text, or warning or cue, no anything appears when shooting.
So these are the steps I did.

1. VF brightness Custom (e.g. 3)

2. When the "Screen is on" or when the "VF is On" I toggle "OVF Assist" (via a customised button)

No message, no anything appears indicating that it was disabled due to "EVF brightness", it looked like it was malfunctioning.

What I expect is: 

When screen is on and Screen brightness is custom the option should work and the simulation take place; I say this because screen brightness doesn't affect the "OVF Assist" .

When "EFV is on" and "EVF brightness" is custom the option should NOT work AND when the suer attempts to turn it on the user is informed/warned. 
Par example the "OVF icon" could be showed as "not doable" when the user tries to enable it (see mockup)




These little cues are simple to do and would help us understand the situation.