For a few years it seemed to me that updates to Photos on Android would silently flip the quality setting down from Original to "High" as in "compressed", so I was never sure if the images I wanted to backup in original actually were backed up or not. I never set it to "High" but it kept flipping back to that.
I raised, flagged, liked and did everything I could on the support forums to get the Photos GUI to report somewhere whether an image was backed up in Original or "High" quality. It went nowhere. And last I checked it was still impossible.
I now treat Google Photos as a last resort approxi-backup and do all my own offline backups to a HDD because I can't trust the metadata. And I'm one of those idiots who even pays for Google One.
(seriously, would a tag like "quality:original" stump the engineering team?!)
Edit: Ha! It's set back to "High" for me AGAIN!
This definitely sounds like a bug worth tracking down. If you're interested in using your account as example, it would be helpful to file in-app feedback including at least the following two things:
1. "I grant permission to look at my account metadata to debug this issue"
2. An easily searchable tag like #OriginalSetting
Google likely assigns these preference quirks to be low priority bugs, which when combined with an under-resourced, unprofitable/breakeven service means it will be eternally neglected.