Maybe it's a mismatch in requirements. For me, I move it into greyscale to give my monkey brain less reason to want to play with it. The intention when it's enabled is that if I need to set a timer or jot down a note that I don't get sucked into the device. When I'm done in a deep work mode, I switch it back to normal screen.

So for me, the whole point is I won't be using it enough to notice eye strain or something like that. If I'm messaging or doing something the device is designed for, it's a benefit for me to be able to have it in full fidelity.