A wild guess : they were concerned with glass front panel drag. They were looking on a way to minimize its size. By relocating the visor close to where it was needed (the leading pilot eye) they could reduce the size of the visor hence the size of the front glass panel.
Moreover, the right handed pilot could use his shoulder blocked on the cockpit wall to maintain his head position during a dogfight. Relocating the visor on one side would hence become natural in a cramped cockpit.
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