@Awesome Donkey,
That's possible it would work a bit different, or it could work better. I think only JRiver's team can really know that. However, I watched this year's MSFT Build conference and they said that Desktop Bridge is basically the same app, only with some minor changes if necessary, so it can be implied that no noticable difference in performance should happen.
EDIT: by the way, that wouldn't really be UWP, rather a win32 wrapped in appx that installs and uninstalls easily, doesn't use system registry, avoids dll hell and is easier to update in-between major releases.