MusicXML can handle the exact timing of the notes, but a lot of software does not support this yet. Finale's import and export tend to handle only limited cases, like placing grace notes on the beat or before the beat.
It would be interesting to know if Notion is exporting the timing information to MusicXML. Would it be possible for you to share a Notion file and the resulting MusicXML file that demonstrate this issue?
VP of MusicXML Technologies