In the Horus Heresy novels, there are Luna Wolves who basically because of Horus’s awesome gene seed become mini horuses, looking exactly like him but astartes sized. Does this still occur in the black legion?
The gene seed is still around, so I'd guess so. A common feature of the gene seeds is that a lot of astartes takes on the visual traits of their primarch. You see this mentioned a lot with some other legions, like for example the blood angels having faces resembling Sanginius.
But a lot of the traitor space marines resent Horus for failing during the heresy, so guess it isn't brought up much.