Hi @matthias22, welcome to the forum and thanks for your report.
The staff actually intentionally designed subspecies IDs to work this way, and have acknowledged that it is not a perfect solution. There’s an open feature request where you can continue the discussion: https://forum.inaturalist.org/t/leading-subspecies-ids-should-change-the-obs-taxon-like-leading-ids-of-other-ranks/139