I don’t think that’s true. GMTI is generated based on the difference between two GM-type radar pictures. The indicator would be based on a threshold of difference data. If the radar is sharper in range or azimuth that would affect the ability to generate a sharp difference bump but it shouldn’t be radial velocity only.
MTR is actually two MTR settings. There is an MTR HI/LO for AA radar modes and an MTR HI/LO for GMT radar mode and they are independent.
I completely disagree. When you look at RL radar GM maps, they have a very poor resolution (especially angular) and are fairly noisy. Comparing those would yield nothing.
Those slides do a good job of explaining what you can see in various radar modes (GMT or GMTI as its usually known ; SAR as well).
EDIT : reading those all the way, there is a technic that ressemble what you describe (slide 48 ). But 1/ this is in SAR maps; and 2/ there is absolutely no way it is implemented in the old APG-68.