Unwanted Display Dimming

Been trying to figure out if I am missing a setting or if this might be a software bug

Symptom: display dims 90% or so during the streaming of a movie for a long time (subjective to be sure) however I have adjusted settings as best as possible to prevent any display dimming.

Here is the set up

Display Settings
MacBook Pro M4 Sequoia 15.7.3
Power Cord Connected
Resolution: Default
Apple XDR ps-1600, I think default
60Hrtz ( because Promotion seems to result in stuttering videos)
Trutone: Disabled
Auto Adjust Brightness: Disabled

Accessibility
Dim Flashing Lights: Disabled

Battery
Prevent Auto Sleeping: Disabled
Put Hard Drive To Sleep: Never

One thing I have not determined yet, is if while having had the camera taped over, and thus

possibly the light sensor whether this has anything to do with display dimming over lapsed time

Also, I have not tested this issue with Mac OS Tahoe

Thoughts welcome