Or possibly if the room is very reflective and the monitor is near a wall, would more or less reflected light as impacted by patch size affect the readings.
LCD displays do not block light completely (thus the relatively poor black level of standard LCDs, which is the backlight shining through). It is therefore fair to assume that what’s displayed on the screen affects how much ambient light can enter.
Could the small gap between the colorimeter and curved monitors cause a wrong black reading because room light may get it.
Room light may affect readings to some extent. Whether that is a problem or intended is up to you to decide (for something like BT.1886, including the effect of ambient to some extent may well be desired), but in either case, if lights need to be on during measurements, lighting should be consistent and not changing throughout the measurements.
I understand for home use and home instruments, these things may not cause a huge impact, but how does the lab scientist treat these elements.