Fascinating picture! I'd never seen that one before.

German research during WWII showed that forward swept wings had some advantages over rearward swept wings. One of the biggest advantages is that a stall begins at the wing root for forward swept wings but at the wingtips for rearward swept wings. This gives the forward swept wings better low speed handling. However, forward swept wings also have some disadvantages such as the desire to rip off at high speed. The X-29 got around this problem by using composite construction.

The Germans did build a jet bomber with forward swept wings (Ju-287) during the war. It was an abortion of a design but it did fly. I suspect that wind tunnel model was just a design study.

There was a German produced business jet in the 1960s called the Hansa jet. It's wings were slightly forward swept so that the spar would be aft of the cabin. One of them used to stop regularily at my hometown airport when I was a lineman there back in 1976. I hated refueling that bastard! It didn't have a center point refueling system, so I had to climb on a ladder to reach the wingtip tanks. With the narrow landing gear, I had to partially fill one side, switch back to the other side for balance, and keep switching back and forth until the tanks were full. The plane kept leaning from side to side as I filled the tanks.

As bad as the Hanza was, it wasn't as bad as a MU-2! The landing gear struts would suddenly compress on a MU-2 and the wingtip would quickly drop several feet with no warning. The usual result was a lot of jet fuel on my shoes. That permanently ruins shoes.