I think "PG" describes something about a child, but doesn't address so many other issues like personality, drive, social skills, and academic level, that it's very hard to predict what a given PG child will need. I know many PG kids at grade level (many discussed on this board). I asked very similar questions with my kids were younger and I was trying to figure all this out, but having anecdotes about other children don't help me figure out what's best for mine.
If I had a happy child at grade level, with maturity typical of his age, who had friends he enjoyed, I wouldn't think about skipping no matter what the IQ score. I think it's hard to plan for what a kid might want later whether that is social fit in middle school or need for more radical acceleration. I've found it works best for us if we deal with the kid currently and adjust later as needed. Skips can be undone, they can be increased, or the kid can give up a traditional path later depending on needs.
Whether skipping makes sense depends on a lot more than intellect. Maturity, social inclinations and abilities, other interests, available schools and school flexibility, peer group in each grade can all matter. A skip from elem to middle school might make a difference in available courses, but a skip from 1st to 2nd grade might not change much. Some kids need many skips in all subjects and subject acceleration or skipping one or two or three years wouldn't come close to the right academic level, so then the kid needs to be with kids much older or needs homeschool or needs to sacrifice academics to be in school with peers. Which works for a given family depends on the family.
