http://kippenjungle.nl/sellers/page3.html
This page says henfeathering is dominant. That would mean a rooster could show hen feathering, and carry the recessive for normal feathering.
There is also the difficulty of selecting which hens have the genes-- you have to work out their genes by the...
If it's important to know, a DNA test is available:
https://orders.iqbirdtesting.com/order-bird-dna-test/
But if it isn't a big deal either way, I would just save the money and be patient. These things usually become more obvious with time (although less obvious in Sebrights than in many other...