Yes, these have been around for awhile. The genetic symbol for cream is \"ig.\" Lower case i denotes recessiveness.
I believe it is common practice to examine show birds for bits of fluff or feather growing between the toes or along the outside of the shanks, and then removing it prior to showing. I would not characterize stubs as being common or prevalent among Ameraucana stock, but it can happen, especially as the result of outcrossing to different strains. Stubs are common amongst certain varieties of Wyandotte and Japanese bantams. From a breeding pespective it is very important not to mate two Ameraucanas both of which carry stubs, as that has the potential of perpetuating a disqualifying trait, and sometimes even creating partially feather legged offspring.