Probably 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 by now currently being there, appears entirely wrong in Upper-Austrian, but I don't know about the Germans. I've also heard about https://bihlmayermedia-bilder.com/urlaub/wir-sind-im-urlaub/