interesting thread. im considering trying some amberlinks. ive always liked a white chicken  but wanted brown eggs. so this cross may be the answer.  
id say there is no white leghorn in this hybrid cross..going by the pics posted......thats just making a visible assumption of course.
and with any sexlink bird.  you dont think a hatchery is really using pure parent X pure parent stock???   course not. my money is placed on both parent stocks are already crossed hybrids. bred to produce the known modern sexlink fowl we all have.  thats why the sexlink hybrids wont breed true.  to much genetic "soup" in the parent stock already.  we could be dealing with a six way cross  MINIMUM  right off the bat with the F1 generation.