It is quite possible that the specific feature shown on the photographs is the result of a gene or combinations of genes which are found among some royals and some other people. There is evidence that a number of different aspects of ear shape are influenced by at least 6 different genes, on different chromosomes, though none are found in mitochondrial DNA. The piercing or partial piercing could easily be the result of one or a combination of these genes, or of another gene which has not yet been identified.
What I object to is the implication that anyone who does not possess this particular feature cannot belong to this particular royal family, or that anyone who does possess it must be royal.
It would be interesting to trace its appearance in family members and others, as has been done for other inherited characteristics, like the cleft chin that appears in many British royal descendants, or the red hair that appeared among the Tudors. I hope that sort of information is being documented in the Facebook page you refer to.