This has nothing to do with anti-aliasing.
All the VR popup windows are “overlays” using a specific VR Overlay API which let’s you render textured quads in the 3D world. The AA is only applicable to the 3D render views.
It is actually because these overlays are rendering at your HMD super sampling resolution instead of the game render resolution (when using <100 TAA render scaling for example) that I’ve suggested the following:
[BUG/FEATURE] EFIS Screens Problems and Solutions for higher legibility
However SU5 is certainly displaying aliasing artifacts on these overlays and there could be many different reasons to this only Asobo knows.
*In addition, because they are not rendering in game, they are immune to any in-game post processing FX and they can also be rendering out-of-sync from the main render thread(s).