That's correct. On a black background, you're likely to pick very dark colours since they feel light next to the black, and you'd avoid light colours because they'd look too bright. On a white background, it's the opposite. With a midtone such as grey, it's easier to pick a good range of values.

Grey is also good for picking hues since everything looks more or less its own hue next to grey, and colours pop, so it's easier to avoid making things too saturated (the opposite end - not enough saturation, has to be checked).

Including what eishiya mentions it a good thing to take into account the time of day and lighting as you work. I work on grey BG almost always but if its very bright I'll switch to black. Its a good thing to do a visual test by switching BG colors white'grey'black and see how its looking.