So I notcied that infantry can't simply hide behind structures made by Bulldozer.
They try to use it not behind it, but on the edges which leads to lack of true cover (I tested it. Guard behind proper cover vs Ober behind this side cover (they have green mark but they obviosuly stay out of cover) and opoosite, Obers behind proper cover and Guard with this side cover. Guard were melted when used "side cover" and they were quite equal behind proper cover so it counts).
Units can't simply stay behind it and use it like a cover, they dance around edges and no matter what, they don't want to hide straight behind.