Always on Display dims during activity

This is how all AMOLED devices function. When your hand is down it dims the screen after time specified 4, 8, or 15 seconds. 

Are you saying that 265 would be full power for many hours of activity? Can you show the video as this is very interesting. 

I think you were right. I made a direct comparison, indeed, and Garmin 265 reduce brightness. Apparently I was mistaken. However, this is uncomfortable, after the constant brightness on the MIP Garmin 7

daytime activities MIP is better but nighttime running AMOLED is better. 

Not in my experience. MIP's backlight can stay on and you can have white backgrounds which I find more readable than Amoled's white on black.

It's exactly the same as Epix 2 for example. AOD means it doesn't completely turn off the display, not that it doesn't dim. If you turn AOD off for activities, it will go dark. If you leave it on, it will dim. It would be bad for both the display and battery life to be full brightness non-stop.

It never bothered me in bright California sun and the gesture works pretty reliably during activities, so I consider it a worthy trade off for much better looking maps and will never go back to MIP. Plus, even dimmed, large data fields are readable. But if it's something that bothers you, as others have said, Solar version might be better for you. Luckily, we have a choice (except for 43mm, apparently).