Spoke too soon. Something about Output 18 (Pin 5) is different. It looks like it fluctuates around 0.5 disarmed and 0 (no fluctuation) when armed. I was going to map Output 18 to AWAY mode.
Output 17 is mapped to STAY mode an is working just fine. I sort of assumed the hookup would be the same, but even the description in the manual that you copied pasted seems slightly different.