I think this story has been around for a long time. I remember seeing an entry about Romanov facial markers in the Rootsweb Romanov forum, dated 2006 but no-one seemed to take much notice.
It might be meant to imply that all descendants of some particular royal ancestor will have this mark, or that some of them will, or that people who show it must be royal, or if you don't show it you are not royal, or that the trait might be the sign of a rare genetic marker (SNP), or something. It all seems seems rather woolly to me.
Incidentally the mark is described as an ear-lobe marker, appearing as a horizontal crease in line with the tip of their noses that leads into a partial peirce mark. I can't see it in any of the pictures but my eyes are not what they used to be.