It has already been asked at the current Lojban proposal, but not at the Esperanto and Constructed Languages proposals, why it would make more sense to have a SE site dedicated to this single constructed (fictional) language rather than one for many using tags as with programming languages on Stack Overflow.
I’d like to ask more generally (but not as general as done here): Is it a good idea to introduce some more broadly scoped languages sites first (e.g. for constructed, Scandinavian or Slavic ones), but not just a single one, and possibly later introduce spin-offs if particular languages prove overly popular?
Take German SE, it’s still in beta because there are too few questions per day, although there are 100 million native speakers of German and millions of learners/learned. It’s at least in the top 20, more likely top 10, of languages written on the Internet. How can any “smaller” language expect to fuel a SE site successfully and sustainably? (Also not e that lots of questions get closed at German SE because they’re simple proofreading or translation requests.) The Russian and Spanish beta sites seem to be in similar situations despite even more potential users. I haven’t checked others.
For natural languages, it would seem intuitive to group related languages, e.g. all Germanic ones except English (i.e. German beta + Dutch active proposal + Scandinavian failed proposal + Yiddish + extinct languages), and we already have a unified proposal for constructed languages.
One drawback of multi-language sites is that not all members (notably administrators) can be expected to know more than one of the languages (and English).