So the technical stuff first: The AOA bar isn't displayed by default. When you get done with an AOA cal, it nominally pops it up for you automatically. Even if that were not happening, you can nominally fix that with the CLUTTR menu. Obviously, if that menu item isn't available, that's a problem.
If you're seeing the red chevron, it sounds like you have the bar up. So you're probably OK. The RV-12 menu lock doesn't affect the unit's ability to do a calibration.
As for the locking issue: The CLUTTR menu button was removed at Vans choice to avoid the inadvertent removal of items that are critical, like airspeed an altitude. They're in the same place as the AOA bar, which isn't nominally used on an RV-12. Unfortunately, the locking of that particular AOA bar menu item isn't possible to exclude individually, and it isn't feasible to change that behavior because of the complexity of that locking mechanism and the way it is implemented. Admittedly, there are some corner cases like this that neither us or Vans anticipated for people that have decided to build their aircraft a bit differently than Vans' prescription. For folks that are making modifications to the aircraft and going experimental, a non-Vans unit (ie, an off-the-shelf D180) might make more sense. Incidentally, unless you're going experimental amateur-built experimental, it's not ok to make any modifications to the aircraft from the S-LSA example, which doesn't have an AOA probe, until it's airworthy. Then you can make the changes. Weird, I now, but true. So in a nutshell, Vans wasn't really expecting to see AOA probes on E-LSA RV-12s. since it's not part of the spec'd design.
As an additional piece of information: I don't believe Vans is generally willing to RV-12 D180s units, and they're the only ones that have the authorization to change this particular feature on your unit. You'd have to follow up with them to ensure this is the case.
In any case, I think you should be OK here.
