As someone with experience with both therapy and psilocybin (while severely depressed), I would guess the psilocybin is the main ingredient in this concoction,

As someone with experience with both therapy and psilocybin (while severely depressed), I would guess the psilocybin is the main ingredient in this concoction, and the therapy is just being added to make the study more palatable, the same way medical cannabis use had to precede recreational cannabis use.