Gfx.WaitForPresent means waiting for VSync and it appears to function as expected.
22.3 was measured to be a little bit slower than 21.3 both in Editor and Player. (Win10, RTX 2060)
However in the provided repro project showed more work on 22.3 than on 21.3. For example, 22.3 rendered SSAO for all 3 cameras and had extra post effects enabled such as Filmgrain.
Properly enabling SSAO for 21.3 made its performance similar to 22.3.
There seems to be a minor cosmetic bug in the project or UI. The UI showed SSAO enabled in 21.3, but actually required a toggling the SSAO on/off to properly enable the SSAO rendering.
This cosmetic bug is not critical enough to be fixed in 21.3 LTS at this time.