I can confirm that the actual pics are not mirrored, only the preview is. I just held up some printed text and took a selfie, the words are reversed in the preview, but are not reversed in the actual picture.
I have seen a mirroring configuration for saved files but I can't remember if it was this phone with Android 11 or my other phone. Clearing the photo app's private storage is worth a try. Maybe it's stuck with mirroring on and there's no UX to change it. If my phone ever gets really weird I usually start clearing storage for the hidden chipset/system apps too.