Yes, it is definitely the cache. If you zoom out or in, you will see the new boundaries … In fact it is really strange to see it alternate between both versions of it as you zoom in and out again across different zoom levels… This was raised a while back as a bug, not sure if they could find what causes it.
https://forum.inaturalist.org/t/modify-location-map-polygon/1698/2?u=kiwifergus