> It contains the OSM data (obviously) ...

Not really. You need to build geometries from raw OSM data (aka the stuff that you edit) then transform those geometries into MVT format adding appropriate attributes from the original data. In general you actually will want to normalize the data and throw out anything that is not included in the vector tile schema you are using. The net result is quite far from raw OSM data in any case.

PS: I maintain a project that stores actual OSM data in MBTiles format for offline editing, and yes proper editing apps have to do the above on the fly and it is the main reason they are not lightning fast.