Oh, certainly if it's a significant gap, more than a car length more than I would normally stop, I'll shift forwards, especially in high density situations (if nobody is behind me and I'm not blocking a laneway, then I'll probably just sit there).

Something to add to the consideration is that I drive standard, so moving a small amount is a lot more difficult for me than most drivers, and takes more active effort. Most AT drivers just release the brake for a few seconds and they can close the gap. I have to release the clutch and possibly press the throttle to ensure the engine doesn't stall... Etc.

I'll still do it, but my tolerance for a gap in front of me is much higher than others.