"I have yet to see a tender towed at 200 meters "
There is nothing in the regs that says you can't use a dayshape with a shorter tow. Since few recreational boaters know anything about a tow, anything that gets their attention is a plus.
If it's daylight and they can't see a towline they may quite reasonably assume the following vessel is just that and not being towed. Who would try to cut between them with only 400 feet spacing? Do you really have to ask? The point is you can't do too much to protect yourself and at the same time give the other guy a sporting chance.