Heewing Ranger VTOL Tilt Servos not Setting to Level Flight when Armed

Plane: Heewing T1 Ranger VTOL (conversion kit)
FC: Matek F405

Hello. I set up the servo output in Mission Planner such that in QLOITER, the tilt servos are vertical. Also, when in STABILIZE the tilt servos are perfectly level. This is when the plane is DISARMED and on the bench.

I then set the plane to ARM and switch to QLOITER. The motors spin up as expected and the tilt servos go vertical. However, when I remain in ARM and switch to STABILIZE, the motors continue to run but the tilt servos do not go back to level. Rather, they go to some angle in between vertical and horizontal (level flight).

This is on the bench. Thus far, I have not flown the plane.

I have read through the Ardupilot documentation, but I do not understand why the tilt servos return to level when it is DISARMED, but not to level when it is ARMED.

Is this because it is not in the air? Is the FC expecting a certain altitude or other parameter, before it returns the motors to level in STABILIZE? Is there different behavior in a different mode like FBWA/FBWB?

Any help / clarification would be appreciated.
Thank you