On the true B. 'clara' s I've seen the petioles have none of the fuzzy, brown tomentum that is on the armatas. Also the leaflets are longer, thinner, and segmented deeper into the leaf. The petiole teeth also seem reduced and further spaced apart which along with the humidity tolerance suggests the brandegeei influence. I think some nurseries will label any extra-blue, droopy segmented, long-petioled B. armata as B. clara without attention to the details which define a true 'clara' or to the purity of their seed source. The native population of clara in Mexico has consistent traits such as the lack of tomentum. If 'clara' is a natural hybrid of armata and brandegeei as theorized then it obviously has the propensity for hybridizing. Any SoCal 'clara' seed harvested in the company of armata could be hybridized, diluting the true clara traits.
Here's the fuzz-free petiole detail from a photo on palmpedia.net:
and petiole detail on armata with the tomentum particularly visible between the teeth. The difference is more pronounced as plants age.
here is B. brandegeei with almost no tomentum or teeth: