I am definitely guilty of staging the trigger.......the way you put it, it may be adding to the mess.
I'd suggest that this messes things up a lot more than you realize. You're setting yourself up to time your flinch with your last trigger snatch.
Last summer I was SO'ing a group at my club's Speed Steel match. Two of the guys on my squad were LEO's using their duty issue DOA S&W's. The one guy wasn't TOOO bad but the other was taking 12 to 15 shots to hit 5 targets pretty consistently. I mentioned that he was staging and snatching the trigger a couple of times. He'd try to correct it but it would get a little better for a couple of shots and then he was back to the bad habits. After the match I offered to show him more of what I meant in exchange for getting to shoot his gun..... plus I was curious about just how bad issue DAO guns REALLY are....
As it happened I got to show him 15 or so shots worth out of his duty mags (the rest of us are only trusted with 10 at a time up here). And I didn't have any trouble getting 15 hits on targets ranging from 8 inch round at 10 yards out to the 6 inch at around 20 yards. When he really focused on a smooth pull with no staging he was hitting one shot/one target too. He couldn't stay for the afternoon round but he promised to work on this more.
Check out your grip compared to this excellent video;
http://www.youtube.com/watch?v=DDZDttBfock
If you're not doing it just like he shows I'd suggest you have room for improvement.
On the question of using a .22 as a flinch fighter? I'm a huge fan of this method. Like you found it's one thing to do it perfect when dry firing but a whole other issue when you know, or strongly suspect, that there is ammo in the gun. I like the .22 as it gives me SOME recoil that I can work on focusing away from fretting over and it gives me holes in the paper to show me when it's all working well.
I also knew that I wanted at least ONE .rimfire pistol so for me it was not a burden to buy one. Apparently it found a soft spot in me as I've got as many rimfire semi auto guns as I do centerfire.
What I'd do with the rimfire gun is load up and work on my style. When I was in the zone I'd switch to the center fire 9 until I noticed the flinch returning. I'd then go back to the .22 and work on the basics. At first I'd get in the "zone" with a mag of .22 and in less than 10 shots of centerfire I'd be back to flinching. So back to the .22. All in all it took me the better part of 2000 rounds of rimfire and likely 500 of center fire going back and forth before the flinch was put away for a while. If I don't shoot for a while I feel the flinch coming back even with 9's and .38's. So I not only shoot rimfire for the cheap fun but for the ongoing practice.
Staging and then snatching the trigger is going to promote a flinch at LEAST as badly as pulling the trigger only to the BANG! and then letting it go. You need to break the focus on both the break and the BANG! Once you can do that the BANG! becomes something you feel in passing as you're focusing on the sight picture and the smooth pull and follow through hold.
It's not unfair to suggest that if you set yourself up to KNOW that the gun is going to kick on demand by staging the trigger and/or snatching at it with a sudden poke that it becomes very hard to tell the little guy controlling the automatic reactions in the back room of your head to just ignore what is coming. But if you can set things up so that the eventual BANG! is a surprise then you can fool him into missing the event and kicking your arm and wrist muscles until it's too late. And that's where the focus on the sight picture and working on a smooth and steady pressure build comes in.