They have lifeboats on ferries crossing the English Channel. That's not because it's physically impossible to swim the channel (it's quite clearly possible, and is done on a fairly regular basis), but because most people couldn't do it, and even if they could the lifeboat is a safer way of managing an evacuation from a sinking ship.

I'm not saying that it is possible to jump from the ISS, just that the presence of a lifeboat doesn't demonstrate that any other evacuation route is impossible.