The tiny Aerolite has only a few gauges, no auto pilot. But let's say I fly another plane without even using the autopilot once.  And then quit that flight and start a flight with the Aerolite, the auto pilot can be on. It will fly strangely until I hit the Z key which sets things right.

I'm beginning to think some planes have autopilots in their configuration files, even if they don't have one on the panel. So a plane without an AP anywhere on the panel still reacts when pressing the Z key as if it did. Every time it starts to fly strangely, pressing Z will correct the issue immediately.

I never thought about that, I do spend a lot of time fighting with the autopilot even in the Mooney Ovation where the autopilot button actually works.

My other favorite pet-peeve is having to hit every key twice. If I take off and hit the G key to pull up the gear, certain I will have to switch to an outside view to make sure that the gear didn't come up, and then hit the G key again.

Meanwhile my aircraft is no longer pitch friendly.

Oops forgot the flaps. Two key presses to bring them back up too.

In FSX/P3D autopilot was either on or off in the configuration file for the plane. if you flipped 1 from 0 turning it on you could then “use” the autopilot using the keyboard commands for the autopilot.

So maybe this is a bit of legacy code?