I noticed that as a non-logged-in user I was able to see and access the Add New tab and screen. I must have missed that piece of logic (public group, non-logged-in member) for that tab. I’ve opened a ticket and will have it fixed in the next release. https://github.com/boonebgorges/buddypress-docs/issues/70
And yes, limiting creation by group roles is definitely coming soon! Maybe I’ll get a chance to do it this weekend – it’s already half-done.