Probably just other usages of "im Urlaub" greater, like "im Urlaub erlebten wir das und das", "im Urlaub hatten wir schönes Wetter" and so on. "In Urlaub" as in presently staying there, looks entirely Incorrect in Higher-Austrian, but I don't learn about the Germans. I've also heard about "auf Urlaub" https://bihlmayermedia-bilder.com/urlaub/wir-sind-im-urlaub/