If you watch the hell stream from about 1hour 10 minute mark, they talk about it. He said that multiplayer would not instantly be in EA. Would be nice to get some clarification to this though. Might be me overthinking it.
Hello,
Actually, he said "split screen will come later", but multiplayer will be in-game during Early Access. I know many people heard that bit wrong.
Here is an article, for example, that confirms what was said :
https://www.standard.co.uk/tech/gaming/baldurs-gate-3-early-access-release-date-a4528321.html