They have a Twitter/X post about an update but nothing mentions the split-screen issue. We need to flood their comments about the issue.
https://twitter.com/baldursgate3/status/1702023390511374743

There's also an IGN article that mentions the split screen is "mostly ok". The more people talking about this in the comments the better.
https://www.ign.com/articles/baldur...-confirmed-alongside-full-support-on-mac