That is not correct as typical remaining genetic problems are not successfully bred out since they are recessive.
The mutt will almost always be healthier than it's parents as it is highly unlikely to have any recessive ailments of either line.
The mutt will almost always be healthier than it's parents as it is highly unlikely to have any recessive ailments of either line.
Two ugly parents will not produce good looking children, even if they are from disparate breeds.
Good looking parents will produce good looking children, even if they are from the same breed.
Muttiness does not create good genes.
Anemias such as sickle cell and malaria are the text book example. Having two parents from the same area means high frequency of them having the same gene. The same sickle cell anemia gene makes one quarter of their children fully anemic and leaves one quarter unprotected from malaria. One such parent makes half of children protected and half unprotected.
Anyone can breed on the dominant traits of genes and talk about looks. Their results are defective because of recessive traits. Thus a first mutt with their line has much higher odds of being healthy even if it's other parent is also inbred. But two cross breeds from those same lines are going to be more likely to produce unhealthy offspring again when compared to fuller mutts.