I had the same question about the hopper sliding around. The article isn't very clear about this.

I would think a loop-to-loop connection with the leader would let the hooper slide around while casting and when the fish hits. This is b/c the leader-side "loop" will want to straighten out and mono-to-mono is slippery (and wet too). With yarn indicators, the loop is generally something that is non-slippery, like a rubber washer or grommet, which prevents it from slipping.

I'll have to tie some of these and see if it works.

Go Giants,
Fly Rod