In mount, rear-mount, and closed guard I actually want the type of pressure I generally avoid when passing. So, why are these geographies different?
The common denominator is I have degrees of influence (depending on specific geographies within the position, i.e. low mount with hooks, high mount, s-mount) based on my legs being around both sides of my training partners body. If I’m fortunate enough to find myself there, it doesn’t matter if my partner traps my arms, gets an underhook, etcetera, because the primary management mechanisms are my legs.
Conversely, the arms/hands are there to attack. Roger Gracie using three different geographies interchangeably @ 2:57-4:02 (low mount to control, high mount to strike, and a finish from back mount top when his opponent rolls):