Thank you all for commenting. First, I am a German OSM mapper not really interested in working in the US region. As stated above, I was asked by a friend who was irritated that his on-the-ground observation notes were closed several times for no good reason, at least for him. I now understand where the misunderstanding came from.

About "personal notes": I agree notes should be useful for all, not a single user. In Germany, there is a power user who spams a whole region with his personal notes, using even a bot to close and re-activate them - and despite opposition from other users, he is protected by a member of the Data Working Group... Glad to hear that in your region the rules are more strict. 
I was not aware that real estate people would misuse notes for advertising, and understand the problem. That clearly is a US problem...

But in this case, it really is an active building site. 
I asked my friend for more info. He told me that, as Starbase is developing that quickly, it would make no sense to mark every building site as such, but to leave the note marker open as a reminder to check again a few weeks or months later if there is newer images, and then add the building - like Fesca suggested.
In the last Youtube RGV flyover I could spot all the disputed areas, this, the school and others, as active building sites and confirming the on-the-ground observations. If spotting something in a recent YT video is not considered adequate enough, just wait.

And last: I do not think my friend will ever contribute to OSM; he was just visiting the region as a space fan, and wanted to disclose a few new things he spotted. After this experience, I think he will refrain to continue. For myself, I usually only work locally and on-the-ground, but will be glad to discuss further and/or help here.