tbh I don't know what to think.
After googling it and looking at other topics on other forums you are left with two opinions.
1. A lighter weight gives a smaller contribution to horizontal lift hence increasing Vmc
2. A larger weight gives the airplane a larger AoA at the same airspeeds as an airplane with a smaller weight, and therefore increases P-Factor, giving a larger moment arm to the live engine, increasing the yaw, and also blankets the tail in more disturbed air from the wings given the higher AoA, lessening the effect of the rudder/fin
These two statements about AoA are taken directly from the Oxford ATPL Principles of Flight book
I'm not a engineer, nor a professor in Aerodynamics, so I only know what people tell me. However I have this from an ATPL course, and to me, both seem plausible tbh