My current understanding is that students can self-assign to "Student Groups" but only to pre-created "shell" Project Groups. I would like the option to allow students to create their own Project Groups to avoid having to make a bunch of empty groups for them to join ahead of time. 

BTW I think this is possibly what 

https://community.canvaslms.com/t5/Idea-Conversations/Group-projects/idi-p/392641

was referring to but the poster never followed up.