> [Python] is embeddable easily via some helpers

You can embed Python, but making it safe to run untrusted code written by users will take enormous effort. Roblox is a platform for easily creating games and playing other people's games. They can't allow those games to pose a security risk to players' computers.

> Not sure how fast it needs to perform once embedded, apparently you know.

You're commenting this on a post that talks explicitly about wanting a faster interpreter than Lua 5.1. Nobody is switching from Lua to Python and getting better performance out of it.