I've seen a few videos of F-22 airshow performances that were next to mindblowing. Definitely more impressive than flanker TVC shows and actually indicative of what it is capable of in actual combat. But it is quite true that these flight speeds do not show everything they are capable of. Some are more impressive at higher speeds but turn rates are limited by human factor rather the airframe. I think a lot of what these slow, post stall speeds are aimed at showing off is flight controls, recovery of speed, and agility even at low speeds. While these things are impressive and "prove" the plane somewhat, they are supposedly not all too often used in actual combat where a pilot usually wants to maintain energy in speed or altitude and trade it for direction whenever he chooses.