Indeed it is -- fixing traits (creating homozygosity) in standard breeds involves intense inbreeding, which also makes normally-recessive and harmful traits muc

Indeed it is -- fixing traits (creating homozygosity) in standard breeds involves intense inbreeding, which also makes normally-recessive and harmful traits much more likely to be expressed than in any natural pattern (inbreeding is normally abhorred by nature). Purebred dogs are far more likely to fall victim to cancers, hip displasia and other ailments that would naturally be selected against.