This might solve your confusion: "The maximum fixed numeric speed limit, followed by the appropriate unit, if not measured in km/h"
https://wiki.openstreetmap.org/wiki/Key:maxspeed



"loads of city roads have speed limits 50-60 m/h but the legal limit is 30 m/h"

Even if that were true, it's irrelevant  to your changeset.

Please provide concrete evidence of these changes, especially the A roads, or I'll be reverting the changeset.