Can confirm that it seems like I also have some 28 words that became Mastered instead of Seasoned 1 despite not being set to Mark as Mastered in my settings. They all have a “first study date” of 22/09/2024 and have never been reviewed.
It seems like the daily sync is marking them as mastered for some reason, because the manual sync I did after my previous post did properly mark things as Seasoned 1 and give me extra reviews after the sync.