Okay, so right now the thing to track is "old bugs". If it's old (I think they're trying to get to a place where 14 days is "old") it should be fixed or won't fixed, but not held on to.
I happened to notice today that one PM assigned a bug to me that she sat on for 20 days, it was opened over a month ago. Another PM assigned me two bugs that he sat on for a week. I sent them to him with "there's no way I'm ever going to fix this" with my reasons why, and he sent them back with "[another PM] told me this isn't true, can you look again?".
But, yeah, 2 PMs were lazy and they just smacked me with 6 weeks of bug age. Of course, if it were any other metric I'd be annoyed they assigned them to me for that reason. I'm probably primarily annoyed at the bugs I'm getting just because I hit 0 bugs, and the PM thinks that I can fix it faster than the actual feature owner. But, guess what, I hit 0, I'm mostly checked out for the rest of this product cycle.