Exactly. The law of large numbers says that 1) over time, a 55% shooter is a 55% shooter, but it also says 2) over any given limited sample, the shooter's performance may deviate wildly from this average, either to the good, as in your Wilt example, or to the bad, as with the unfortunate Ms. Hrynko. I am sure that Wilt also had games in which he went ohfer, and that Ms. Hrynko will have games in which she will shoot 100%. This in no way refutes my contention that good free-throw shooting can not be learned, or notably improved upon by practice.
My whole point is that those who say that anyone is a good/bad ft shooter from practice/lack of practice is simply misled. Practice does not help.