Not talking as a hybridizer and I might not really reply on the information that you need, but my Sempervivum 'Rita Jane' in 3 years has looked different in all 3 years, maybe because the clones where moved from propriety to propriety and because quite frankly the soil and weather were not identical.
Most importantly it seems to not really have the coloring that Erwin shows on his website for example. If of course looks like Rita Jane especially because it has the special growing on the leaves, which sometimes it just does not have the entire year.
While this is anecdotal to generalize it is a good generalization for the Sempervivum 'Rita Jane' I would think.
So one could miss the features of some cultivars because they always grow in the same conditions, here I mean the sun always hits the same for the same hours and the substrate composition is not too different from another.
For example I see lots of non-close huge Sempervivum being posted by people, unquestionable very long leaves with barely any thick and short taper at the end of the leaves, in my experience that happens when the substrate is rich, there is constant good moisture (not too much to kill the plant, but not too little to stop it's constant "spikey behavior") and there is never too harsh sun on the leaves for too many hours.
You can even see this when someone has lots of cultivars and many of them grow pretty much in the same fashion, so you can automatically deduce that there is a massive environmental influence rather than specific feature and characteristic of various cultivars.
For example I would think in such environment like I was describing before one would not be able to concentrate on selecting other features than special coloring as something like a beautiful balled up with ultra thick leaves like 'Picasso' can be will not get those characteristics in that environment, but rather have long leaves with pointy ends and grow not that compact.
Similarly if the soil is too rich and wet for too long certain tiny arachnoideum lose that perfect ball shape, that is perfectly closed, which let's say I am looking for that closed-up shape those tiny plants to have, as when they get a ton of them, they look like soap bubbles.
