I’m using both Bambu Studio Beta v1.9.0.60, and OrcaSlicer v1.9.1. I have used both apps for almost a year due to different anomalies that exist in both apps (I find that I have to use one or the other to provision workarounds). And, what I describe below I do not know if such existed in previous versions of the apps, but it does exist in both versions of the apps that I reference above.
By design, the “Strength>Advanced>Infill direction” angle also inherently controls the angle of the “Strength>Top/bottom shells>Top shell layers” and the “Strength>Top/bottom shells>Bottom shell layers.” However, this is not the case re the 1st layer of the “Bottom shell layers” which appears to be hardcoded to 45˚ of the object’s orientation. E.g., if the object’s orientation is set to 0˚ on the plate, the 1st layer of the “Bottom shell layers” prints at 45˚ relative to the object (and plate), regardless of the “Infill direction” angle setting. And, if the object’s orientation is rotated to 45˚ on the plate, the 1st layer of the “Bottom shell layers” still prints at 45˚ relative to the object (but, of course, now 0˚ relative to the plate).
However, the remaining “Bottom shell layers” do respect the “Infill direction” angle, as do all of the “Top shell layers.”
Presumably this is a bug.