I familiar with this approach. Same people also don't like people that breed cory albino from the same reasons. In the past I bred many corydoras albino, they were super strong and healthy.
"Just experience of myself and dozens of people I have talked to"
You bred hybrid corydoras successfully? And thus dozens people as well? And they were not healthy. As far as I understand and saw in my tanked is not common that different type of corydoras will crossbreed. Also in the same lineage.
I dont say that my plan is to cross breed them in purpose, but Im tring to understand from where come this assumption that the offspring won't be healthy.