it is upto vite team to decide between "open source" or "open core". from my perspective, there is no data to say otherwise, so your "from outside" translates to "In my opinion, but I take no responsibilty for it"
they certainly get to decide which label to pick for their projects (vite and vite+). you should complain if they do not act according to their choosen labels. but there is nothing done at the moment to complain about.
https://en.wikipedia.org/wiki/Open-core_model