True tone is not the issue here, even if its turned off. It’s just the 11PM is yellower than the xsmax. That’s my issue also before but I tried to compare my unit to other display unit in Powermac and apple retailers and it’s just the same. There is no problem with your unit. They just made the 11PM yellower than the xsmax. Some says because of OLED.
Go to Settings
-> Display & Text size
-> Color Filters ON
-> choose Color tint
-> Play with intensity (better to set to “0”)
-> Play with Hue (better to set to 40-50% or just near center)