Feather-sexing is genetic--it doesn't always work. It's like color sexing, but with feathers.
The first one looks like it might be an EE. I didn't watch the whole thing, but the second might be a Black Sex Link. I've never had one, but many females grow up to be black with some copper on their breasts. I'm not sure if the copper would come out as chick fluff, but it it does, then you've got a BSL pullet.