I'm afraid that you will come across a lot of inconsistencies around bus infrastructure. A lot of it was mapped a long time ago and some access tags and tags expressing other traffic restrictions in OSM have evolved since then.

As an example of that, if bus routing software trusted the maxweight=* tag, you'd have added headaches - there are over 15,000 of them in the UK, almost all of which should be maxweightrating=* (bridges and weak roads) or maxweightraing:hgv=* (mostly residential streets).