If a person recovers after LL, then he is by definition back at 100%. Then he can also attain proficiency in sports through training like any other healthy person. And don't forget that that same person has longer legs than before. If anything, he can go back to over 100%.
All you who measure a specific level of athleticism have forgotten that this is a volatile physical condition that purely depends on whether you are doing actively sports right now or not.
I can consider athletic people who did not do LL still less athletic than me, if I do perform better than them in certain categories. This 100% value is such a vague number, and it can be shaped by the effort you put in.
The average person who can not even do 3 pull ups is more disabled than a person who finished LL but can do x times that number.
Let's say someone goes hard on leg exercises more than ever before after LL, he will perform better than before LL, just because he chose not to do leg exercises before LL, and after LL he did. It simply depends on how much you work out and how hard you go at it.
You can get back to 100% and even exceed that previous level, BUT you need to fully recover from the surgery and end up with a normal anatomy, that is not less restrictive than before. And that may just be the reason why some people won't get back to 100%. Just doing one segment can be more detrimental to your anatomy than doing two segments in terms of proportions.
People who do both legs moderately and had shorter legs relative to the size of their upper bodies are the best candidates imo. It's not a black and white answer, and depends on the effort after the surgery, definitely.