Well, all NAA's and LQ's flags are being pushed to the LQ review queue. I'm a 20k user but that doesn't mean I want to use my delete votes on 0 scored answers, in fact I cannot vote on them outside the queue. Then why are my votes used?
Don't really see the problem here. You get X number of delete votes per day (between 5 and 30, depending on reputation - so by the time you can vote to delete answers, you'll have at least 15). You can use them on whatever you want: questions or answers.
Review gives you a bit of a boost by allowing you to vote to delete 0-scored answers. This is done just to save you the step of having to down-vote them first and then vote to delete.
20K+ users can clear out low-quality reviews faster than normal users, as it takes only 3 votes (vs 6 recommendations) to delete posts. However, if you use up all of your votes for the day you'll only be able to recommend deletion, and your recommendation carries no more weight than anyone else's.
If you're regularly running out of delete votes and notice a backlog of either questions or low-quality posts developing (either inside or outside of /review) then that could be a problem.