Those are fun (I’m being a tad sarcastic here). I see those a lot since we have quite a few native rhododendrons in our area as well and it appears almost every cultivated hybrid rhodo or azalea gets labeled as either one of those or the apparently ubiquitous R. ponticum, which actually shouldn’t be here at all. Not sure this will ever get sorted out since it’s so hard to tell e.g. Catawbiense hybrids from actual R. catawbiense just based on photographs. It often comes down to taking a guess based on location and habitat.
There’s a lot of planty and shroomy wild stuff to find as well: Mosses and lichens on tree bark, weeds in the planted beds, mushrooms popping up under trees etc. A lot of these are a challenge to ID though and I know this results in lots of observations of dandelions, clover and such from the same location. But as others have already pointed out, tracking invasives and their flowering times can be very useful.
In addition, for some classes or student projects non-wild observations of plants may actually be useful/desired. We have a phenology garden on campus, for example that is part of a grant-funded multi-university educational project tied to climate change questions. We also have several student research projects going on that look at plant-pollinator interactions. Knowing what plants the pollinators are visiting (even if those are cultivated) is important data for these. I think it really comes down to this:
I’ll add to this that the first training target are probably the instructors training the students. Usually there is less turnover in that group of people compared to the students they’re teaching. In our first campus-wide BioBlitz, we had a ton of cultivated plant observations that weren’t marked properly. This number has come down as people on campus (including participating instructors) have gotten more familiar with iNaturalist and how to introduce it to students.