Some of those Gemini EVAs lasted for hours
They weren't all as short as Ed White's EVA. Until Aldrin's EVA (Gemini 12), most of the EVAs after Ed White's were near disasters. The astronauts lacked adequate hand and foot holds, so they thrashed around as they tried to do anything. Perhaps they didn't get space sick because the orientation of the spacecraft to the horizon was more or less conventional, or perhaps it was because they were so exhausted trying to do even simple tasks.