Based on the fact that they(phylos) haven’t found complete homozygosity at the genetic level, in the varieties they’ve tested?
If you tested all Sumatran tigers for example, of course they would not be completely homozygous at the genetic level. Does that make them a polyhybrid species?
I’ve grow more than a handfull of varieties that displayed homozygosity in actual practical experimentation. So I find these claims confusing.