I don't think it's the jackplate so much, as it is the skeg setting
forward of the prop and lower unit. That skeg setting in front of
the lower unit splits the vegetation or pushes it down, leaving
space for the prop to get some bite and water to reach the intake.
The skeg doesn't make an outboard a mudmotor, just an alternative.
I always preferred something like an aircooled Lycoming
in a cage with a fan to get me through the heavy vegetation.