[GERGE]

You are most likely correct. But there is a marked difference between previews from Kobo and book I bought from Google Play. The difference is in Kobo's books line-spacing, margin and font-family informations are clearly missing on the body parts. And everyone here should agree that these are the biggest problems we face with epubs.

They probably have an automated process filtering them out while converting submitted epubs to their own kepub.

This is a good way to go about it, I think. But might be too intrusive in some books. But until the publishers learn how to create better epubs, I don't see any problems with this. Especially as we still have access to original Adobe epubs. I checked some books from problematic publishers like WotC, their epubs are still bad while kepubs are good.

PS. They also sometimes add spacing between paragraphs that does not exist in the original epubs they give.