It was working well before 13.2.
From iOS 13.2, adding any kind of overlay (e.g. MKTileOverlay, MKPolyline) will cause all exisitng overlays on the map refreshed, flickering.
Confirms my experience as well, reported under FB7451880 (performance regression) and FB7455392 (tiles cache not working in iOS 13?). I think we should be all reporting, otherwise these issues might stay forever.