I am not really convinced by the explanation of Strida EU, because, on my LT, I can feel more drag from the freewheel the day after I have been riding in the rain. So I would guess that some water or mud gets into the freewheel and corrodes or contaminates the internal parts. This increased drag disappears after 3…5 km.
Nevertheless, the drag is much higher than on a standard bike. When I was a teenager, I had a cheap BMX that I was riding on muddy paths. I never experienced drag from the freewheel, well from the chain when it was dirty or rusted.
Is the Strida freewheel design so much different from the one of other single speed bikes? If yes, is it because of the one sided support of the wheel?