Why can't multiple children be rendered into a destination?

This commit removed that functionality: https://github.com/cloudflare/react-gateway/commit/4d9f6612dcae0ee0285687d3e0d2ab2472fabe53

I'm curious to know why it was removed and to find it if it could be brought back.
Would be very handy for my use case.

I might be able to do a PR if I understand the issue a bit more.
