Thank you, that's a very interesting info! It might be useful when trying new devices.
I've quickly checked the square on some of my devices:
iPhone SE 1st gen - no logo
iPad 2018 (6th gen) - no logo
Windows desktop (HD 2500) - no logo on either display
iMac 27 2017 - most color profiles show the logo, but many others don't. For example, "iMac" profile (default) shows the logo. HD-709 that gave me the least eyestrain doesn't show the logo.
I'd like to add that the test square is very unpleasant to look at on any screen. Apple are doing something very wrong with their graphics. No new Apple devices for me, definitely!
UPD: iMac is the device that gives me the most eyestrain (nervous strain) and that I cannot use with any settings.