yeah, sorry for that. all i know is that, from my experience, an unfendered small wheel folder is considerably messier in the rain than an unfendered full-size bike at equivalent speeds. i do not know all of the science for why that may be. it just is what it is.

but it doesn't much matter because, as has been pointed out multiple times now, fenders are a very wise investment for any bike that's ridden in inclement weather.