In general, jr devs are net-negative. (If they're not, they're not junior! promote them!). They are an investment, they are learning and growing. It will take a senior longer to review, mentor, and coach them to a PR that the senior could've gone straight to that same PR. The whole point is that eventually you've grown another senior dev who will return big multiples on their compensation.
This sounds like you're just going to be spending sr dev time reviewing and rejecting, to have de minimis backlog items (there's a reason they're in the backlog and not prioritized) fixed, and you're not even growing a senior dev, which is the whole point.
Plus, IME most companies carry so much cultural context that being exposed to it for exactly 1 ticket + not having inside people to ask questions means this will be an uphill battle.