They're all definitely genuine unreleased GW sculpts, and as noted they're all on the CCM wiki.
If anyone wants to see other pics of the marines, I have all of them and can post them here if you like. I've been collecting unreleased minis for over 20 years, and managed to get all of them from legit sources.
Lots of reasons why minis don't end up released: not quite up to scratch, wrong weaponry or size, training sculpts that were never meant to be released, or just general chaos at GW/citadel in the early days. I don't know the story behind all of these, but the banner guy couldn't fit into a blister so never made the cut.
I wouldn't recommend that particular ebayer though - just my opinion based on what is sold and the dubious quality of a couple of supposedly legit unreleased minis I bought. He's not Jason Lye - Jason sells legit stuff.