Let me give you an example to illustrate why I think the current industry definition of "cultivar" is a poor concept.
By definition, any plant whose morphology fits the description of the cultivar can be distributed under that name. Imagine if you discovered that (and this is a purely manufactured example, so don't panic) you purchased a plant of S. 'Leah Wilkerson' only to find that there were seven genetically distinct plants in commerce being distributed as 'Leah Wilkerson'! Now imagine how you'd feel if you discovered this after having acquired it for hybridizing purposes, and you also discover only one of those clones has worthwhile breeding abilities, and the others are only mediocre breeders. What if you'd had the plant for years and already used it in hybridizing and were frustrated by the fact that other people you knew were making amazing treasures from their plant while all you got was junk! Well guess what? You didn't get the same plant they got!! As long as the plants look right for the cultivar description, they don't even have to have the same pedigree!
As I say, this is a fictional account - I think it's safe to assume there is only one individual being distributed under the 'Leah Wilkerson' clonal designation - but this is a scenario that has actually played out in ornamental horticulture, with other genera. Allowing multiple clones to meet the requirements for the term "cultivar" is a terrible idea for the consumer. But it wasn't meant to benefit you, it was designed to benefit the industry that propagates and distributes the plants.