Originally Posted by soyabean

Think about it.

If the bosses are on the frame's tube, it's impossible for it to be also fastened on a turning handlebar and fork.

It's just bumpers down lower on the tube that will keep it lifted.

This is actually the safest way to mount something to the front.

Usually it's a basket or rack on the bar/fork, and as you steer, so does the entire weight of that cargo.