Interesting information, and it may explain something that I noticed recently. I am 4 1/2 years out, and if you asked me, I would say that my resurfaced leg is just as strong as my other leg. However, recently I was doing one legged step-ups onto a box with light weights in each hand. I was surprised to discover that my resurfaced leg could do only half of what my other leg could do; 20 versus 40+ reps, while carrying the same weights. I do not notice the difference when doing two legged squats, one legged shallow squats, sprinting stairs, or skiing, but the difference in the one legged step-ups really surprised me after all this time. I think that the difference in this exercise is that it really relies on all of the glutes around the area of the surgery, as opposed to quad and hamstring strength that would be less affected.
Your explanation might apply.