I think QHD+ is a little more ambiguous, as it could also reasonably be used to refer to taller displays (16:10 display at 2560x1600, for instance).

Also, annoyingly enough, QHD itself can stand for "Quad HD" or "Quarter HD", the old smartphone standard of 960x540, which admittedly has pretty much entirely fallen out of use

Isn't that qHD?

Today, it is. But humans are usually not very good at paying attention to the case and machines are too often very bad at preserving it (the best — or should I say worst — example being search engines). And that's without even taking into account the fact that the need to distinguish both didn't exist before QHD was a thing and that most people have no idea there's ambiguity at all.