For approach speeds for a tricycle 172, I will fly a speed which will decrease from 75 KIAS to 55 or less KIAS. It depends where I am along the approach. I sure don't want to be sitting a half mile back, a few hundred feet up, at 60 KIAS, if it quits, a neat glide landing is not certain. And, I don't want to be crossing the threshold at 75 KIAS, unless I have a very long landing in mind.
When I train in a 180 series amphibian, the glide approach speed will be 80 KIAS until the landing surface is "made". I imagine I'd fly a 172 amphib similarly. If your instructor would like you to fly a 172 at 60 KIAS half mile back on the approach, ask him/her this: With a planned touchdown point identified (and stated) far down a longish runway, demonstrate a glide landing to the surface from crossing the threshold (obviously high) at that slow speed.
If I need to get a plane into a very short runway, it'll be a 1.1 to 1.2 Vs0 approach carrying a lot of power, but knowing that if the engine quits before I cross the threshold, a crash is very likely.
Don't fixate on one speed. Fly a profile which will keep you most safe further back on the approach, and get you across the threshold at a suitable [slower] speed to touch down shortly after - that is not one speed, it's a planned deceleration, as you descend. If in doubt, the minimum speed you should fly farther back on the approach would be Vy, because from that speed, a good glide entry is possible in the case of engine failure.