So don't do it in parallel.
Completely park other tasks, spend time on the review and record that time appropriately.
There's nothing wrong with saying you spent the previous day doing a large review. It's a part of the job, it is "what you're working on".
You might as well go into HR. Everyone knows reviewing other people's PRs is like nurturing their kids at the expense of your own.
Well, then just don't play the game. Make a decision in the team, that everyone accepts everyone's PR immediately without any review. At least you won't have to wait.
I'm semi-retired now, but I spent most of my career at a Bell Labs-caliber place (I was the dumbest person there) before "PR" and "code review" became part of the lexicon, and yes, everyone was good enough not to mess things up too badly.
I don't understand what you're trying to say.