I rarely snatch grip DL off blocks, but I think in any case that it's a deadlift like any other. You'll have to keep the weight under the scapula. If you try to push the shoulders more forward to get the depth, it'll "correct" back to straight under the scapula as you stand.
I haven't checked this with video. But I know when I set up this way, I just have to squat down further, not bend over further to get the bar.
Hope that helps.