I can’t see why they should be wrong.

How do I know that I am really allowed to lead a horse there? The sign (title “Verbot für Reiter” = “ban for horse riders”) does not say this, it only forbids riding (AFAIK).

DE:Verkehrszeichen in Deutschland - OpenStreetMap Wiki and Verkehrszeichen Tool - OpenStreetMap recommend horse=no for (and bicycle=no for 254) and almost everyone seems to do it this way, otherwise we would have many more horse=dismount tags in the database. I use horse=dismount only if there is a sign similar to e.g. File:Reiter absitzen, Pferde führen.jpg - OpenStreetMap Wiki

Interesting. This contradicts support vehicle=* tag · Issue #378 · openstreetmap/id-tagging-schema · GitHub