Hello (new to this forum).
I'm not sure Face command is working as intended. I find it a minor annoyance I always have to select the last waypoint to set a facing. Then looked up the command it in the manual to see if it says anything about it. Turns out i don't have to have the waypoint selected:
Then I tried it with a unit "not moving" but about to and it did not work. Okay maybe it mean it literally, the unit has to be moving when I do it. Same result. Turns out it picks the direction at the time you give the facing comamnd, and then applies it when the unit stops moving. That is, it is relative, not absolute, contradicting itself. Maybe I misunderstood, but then it provides an example:
Say I have a unit SW of a building. In my testing if I order a unit to move north, such that it is west of the building, and I place a face command on the building (without a waypoint selected) my unit will face NE, where the building was in relation to the unit in the beginning, when it arrives. The example above suggest the unit should turn and face the absolute position of the building, thus face east.