I kind of have a similar question, because I don't think syncing the play count from MB to GMMP is possible at this point.
If I understand correctly, both GMMP and MB stores their play counts in their own database, not in tags.
By using wifi app, MB is able to "read" GMMP's database and check how much the play count value has changed, and modify its own database incrementally.
Since GMMP does not "read" MB's database, it doesn't reflect the play count value shown in Edit > Properties > Play count.
I think the same happens with the date added, modified, and last played as well.
Steven, am I understanding this correctly?
Is there a way to let MB "share" or "write" its database into GMMP?
Or is it up to GMMP to implement such feature, if it's even possible?