Well, as mentioned, it isn't always. I've received about 75% dam on top. The other 25% have been sire on top and as mentioned by JAGS, dam on top is pretty chin specific as many other breeds put sire on top (including dogs) so anyone who had prior knowledge to that before making chin pedigrees may have made theirs more like another animal. Generally breeder specific, so if it's not listed call and ask. It's not worth messing records up for long term. Records are only meaningful if they're accurate!