It sounds to me like the relationship between dev and main is maintained implicitly. At some point dev and main were the same, and from there, any delta that is applied to dev is eventually either applied to main (if it passes QA) or removed from dev (if it fails).

One more question. What if instead of this dev branch people just asked the QA system to run on their feature branches? Would that generate too much work?

I'm imagining that the flow you describe is some kind of convenient or less expensive version of that.