Usually, if you have a spoiler axis bound to your control, that usually overrides the auto-spoiler deployment. It’s not an SU6 specific, though. I’ve had this problem since I got my TCA Spoilers Addon.
If I bound the spoiler lever to the spoiler axis (as default profile), when I arm the autospoiler, it doesn’t deploy on landing as well. When I investigate it, what I found kind of makes sense. Because the actual position of the spoiler lever is constantly feeding the sim with the spoiler axis position. So if the lever is at the retracted position, it will always tell the sim to have the spoilers in the retracted position regardless. That’s why auto-spoiler deployment gets overriden by the axis position, because as soon as it starts to deploy, it receives a command from the hardware telling it to keep the spoilers retracted due to the position of the lever.
Same thing applies when you bind a virtual button on the spoiler lever with the spoilers axis bound as well. You can arm the autospoiler on the first detent or virtual button, like how Boeing arms it, but doing so will also open the spoilers at 20% because that’s where the auto-spoiler arm position is. And it will stay at 20% deployed until you move the lever again.
This is why I removed the Spoilers Axis binding from my hardware. Instead, I use digital input commands. Retract Spoilers on one position, Set Auto-spoilers arming on another position, and Extend Spoiler on the last position.
That way, you can still retract and deploy spoilers manually (although it would only be either 0% or 100%, and nothing in between). But you can position the lever into the arming position, and the sim will no longer receiving any axis position input (because we already removed it from the bindings).
So if you’re also using a different hardware, if you want to bind auto-spoiler arming, remove the spoiler axis from the hardware and just use Retract or Extend spoilers command.