If I wind the dial in a bit, so as to increase the (low speed) damping, the fork will bob less when I’m stomping the pedals, but should still suck up the (high-speed) bumps?
Kind of; turning the blue dial adjusts the size of a hole in the damper. This can be adjusted from fully counter clockwise (fully open hole) to fully clockwise (hole closed).
With a medium amount of this blue dial (LowSpeedCompression) set, you will get excellent performance whilst riding berms, braking, etc but the fork may not be able to let enough oil through the damper to handle bigger hits (this is called spiking). This is where HighSpeedCompression comes in.
As I said above, the only HSC adjustment available on MotionControl forks is the floodgate adjuster. You can open this almost fully (few clicks from fully anticlockwise) and if you hit a large bump, it will open up and allow more oil through the damper.
Thus, you can have a decent amount of LSC controlling the movement of the fork when not hitting bumps (eg bob, cornering, braking etc) and a different amount of HSC allowing the fork to actually move quickly enough to absorb bumps without spiking.