I learned this method from Chris Perkins several years ago. He does 2 legs on most of his competitions bows but does all 4 legs for added security on his hunting bows.
I just do 4 or 5 half hitches on opposing legs and don't have any issues with the peep moving on slippery bloodline strings. I don't see a need to tie all 4 legs. But that peep ain't Goin nowhere!