When a PR is updated (with new commit changes), more reviewers are added!
Opened a PR with 3 reviewers (or maybe 2?) and received some comments/stuff to fix.
Pushed to the branch with the fixes, and got the tooltip from the edit button to "update" as changes had been detected.
After updating, there is now 6 reviewers on the list!
I think it automagically added the 'suggested reviewers' when it updated the PR :(