I think that really speaks to two things that we now know to be staples of how things were done then -- one, they weren't quite thinking of these storyworlds and characters as an enduring franchise yet, and two, relatedly, they were firmly set on clearing the roster and introducing a new cast
Another interesting feature of its time was that this action wouldn't be accomplished with just a clean reboot that left the original alone, like comic titles later starting with new #1's (also not something as common then as it would be later). They would weave it into an ongoing story, writing off the existing cast with some finality to make room for a new batch. It's bold but wasteful, like how Ditko would cut up old comic art boards as scratch paper or whatever -- the value we see in hindsight wasn't ascribed to it just yet. But yeah, the so-specific coincidence of it being a redeco Optimus Prime with a different trailer HAD to have raised a question. Even if the response was "so what, we've released retools as new characters in both the first few years if this thing", someone had to have asked about that.
Honestly rather like how it turned out. And in the 80s, when background and other relevant information took longer to get places, it made for an interesting experience.
Only seeing the Ultra Magnus character in the movie made me familiar with a cool-looking new big guy leader type with a great design. Didn't even clock he was a car carrier at first; this only became clear after a few rewatches (which didn't occur until the early 90s) since he transformed so rarely in it.
Meanwhile, not having been in a socioeconomic bracket to really be going to toy stores that often (and this being an era prior to local saturation of shopping centers), I'd never actually seen the toy. Not even in catalogs i don't think (that was one of many fun catching-up discoveries in the "we have internet now" era). So I was (ahem) primed to be hyped by playground talk from kids who had a brother who had a friend who had Ultra Magnus and said the toy came with a free "ghost of Optimus Prime" in all white, which sounded like the coolest damn thing.
Of course, even without all of that, Ultra Magnus as a new city commander character is still far preferable to Optimus Prime with New Hat (mind, I totally understand why the toy companies would prefer the latter).