Those notes are clearly slurred. Not every single one to the next, but there's a slur over every upbeat phrase until the downbeat.
Listen to how different the articulation is from the first and second time of the horn theme. The second time it's more articulated. I haven't seen the score, but I presume the first time is MF and the second time F.
And, of course, comparing to a live recording isn't always fair as 2+ musicians with staggered breathing will always be different from one single horn patch.