How do I control rotation speed with an analogue stick?

Video attached to show what I'm doing.

I have a microchip attached to a sculpt, which has a camera and some logic in it. I'm trying to set up an advanced mover and an advanced rotator to allow the player to move around freely using the analogue sticks. Really I'm just trying to emulate the default camera controls, but also move a load of gadgets around with the camera.

I'm taking the controller analogue input, splitting it into X and Y, then feeding that into the mover/rotator. For the mover this behaves exactly as I expected it to.

The rotator however seems to turn toward where my analogue stick is pointing, rather than using the value to modulate the rotation speed. This includes changing rotation speed when I point the analogue stick up and down, which makes absolutely no sense given that I explicitly split the X and Y, and don't use the Y value.

I get this behaviour regardless of the local space toggle being on or off and regardless of the blend mode used on the port - overwrite, modulate and blend all display the same issue in the exact same way.

In the video, once I go into test mode, I'm just pushing the analogue stick all the way to the left, then all the way to the right, then all the way to the left again. Instead of getting a constant rotation speed as expected, it turns to face the direction I'm pushing the stick toward, then stops.

What the heck is going on here?