This was my thought exactly, but evidently Kevin told the poster (OWAL) that he really thinks it's a pearl (homozygous HGW) ...I can't help but wonder if it is something else, though, since he says directly in the videos that all of the pearls are "byproducts" of breeding two animals with the HGW gene, so there must've been more to the parents than just straight HGW x HGW ...
Or, maybe the lethal recessive gene is just linked to the HGW gene, not a pleiotropic effect of it, and he finally hit on the homozygous HGW without being homozygous lethal! (That would be pretty awesome -- the first homozygous HGW cross in MABalls's video is rokken!)