I understand that when importing midi files Dorico preserves the played note duration and when importing xml files Dorico preserves the written note duration.
As for the midi velocity I would expect a similar behaviour but it seems that imported xml files maintain their original velocity. So, in order to have a fixed velocity (as if notes had been typed and not played), I headed to the “Reset Playback Overrides” command in Play mode but it doesn’t seem to reset it.
Dorico does not import MIDI velocity from MusicXML files, even if it is specified in those files (which it can be, but rarely is).
How come I can see columns with different height in the midi velocity editor? Before exporting, just in case they could trigger the interpretation, I checked that the original file had no dynamic indications.
Check the humanization settings in Playback Options.