assuming a lot of his check back range is Tx or worse pairs, JJ-QQ, and some A high hands that are looking to show down, you almost always only have 2 outs vs. his calling range on that turn w/ 55, where a hand like AJ has a substantial bit of equity vs. a lot of his range. Also, there is a much better chance you can show down the best hand than if you have a hand with no pair.
My point is I doubt those hands are in most people's PF range against a tough CO.