Perhaps just other usages of "im Urlaub" amplified, like "im Urlaub erlebten wir das und das", "im Urlaub hatten wir schönes Wetter" and so forth. "In Urlaub" as in already staying there, appears wholly Improper in Higher-Austrian, but I don't find out about the Germans. I've also heard of "auf https://bihlmayermedia-bilder.com/urlaub/wir-sind-im-urlaub/