Well I'm not exactly sure, lol.
I'm definitely using them to get used to handling heavier weight, and they are also strengthening my quads and lower back.
I'm about 9 weeks out of a PL meet now, and will probably open with something like 500 then make 30-40 pound jumps from there. I'll sink the squats at the meet, but to prepare for that I'll probably only take a couple singles to proper depth with my opening weight at about 4 weeks out.
If I took all my squats to proper depth now, I'd have to use a lot less weight and my lower back would also be wrecked pretty much all the time (no thanks).
Also noteworthy (perhaps) is that I haven't deadlifted in over a year, but on Friday (the day before I did these squats) I worked up to a very easy PR single of 565 with just a belt and an over/under grip. In the process I tore some soft tissue in my back though, near the insertion at the armpit (ouch!). It's a bit bruised up now, but seems to be healing alright.
If all goes well I should be able to pull off something like 560/340/600 at the meet, without a squat suit, bench shirt, etc.