Yep, Standard Site is a meta lexicon that is a wrapper for disparate other ones.
I’d say the primary goal(s) are to collectively develop shared lexicons, sharing approaches to lexicon development, and some evolving governance tools over how to do that.
LC does not want to stand in the way of defining new schemas! But rather than everyone having to figure out how to start from scratch doing things collectively, having more tools over time, including a “default” domain.
Independently from your comment, I just invited the Evnt folks in here to discuss updating the community lexicon → Kicking off a dedicated space for discussion for Calendar, Events, RSVP
Multilingual is a great example of something that EVERY lexicon is going to have to figure out an approach for.