That's just a VSD, but using the common idea that the "maneuvering fins" of the VSD are like the X-Wing's foils and lock/unlock instead of being a solid piece of the infrastructure.
I've never been able to find an official source with that setup, but If I had to guess, I think it's because Evilljedi made them that way on his Warlords mod model, which then become ubiquitous in EaW mods because he free-released it and very few mods made their own models, so anything he did stuck. Then, when people started making new models, his became one of their references, which reinforced that. So when the guy who made that searched for references, that's probably a lot of what he found.