Right now there is just a global stats version, works well if you change the stats itself in some way (so all maps need to re-run), which is what it was likely designed for. If you do something like adjust the zones on a map you either have to re-run stats on all matches for all maps or won't get those stats updates for existing matches. I have code so that if a zone is missing in the match stats cache to flag the match for re-running stats. This would allow you to make a minor name change to a zone (or add a new zone) if you wanted to force only the matches for that map to update.
If the version was per map though you could increase it on a zone update.
Right now there is just a global stats version, works well if you change the stats itself in some way (so all maps need to re-run), which is what it was likely designed for. If you do something like adjust the zones on a map you either have to re-run stats on all matches for all maps or won't get those stats updates for existing matches. I have code so that if a zone is missing in the match stats cache to flag the match for re-running stats. This would allow you to make a minor name change to a zone (or add a new zone) if you wanted to force only the matches for that map to update.
If the version was per map though you could increase it on a zone update.