The volume here isn’t excessive. You’ll do 11 sets total for large muscle groups (the one exception being shoulders, for which you’ll do 15) and train each bodypart once a week. Reason being, to pack on tons of mass you need ample recovery time. Doing endless sets in each workout can easily put you in a catabolic (muscle-wasting) state in which lean tissue is broken down, not built up. Gaining 10 pounds of muscle in such a short period requires the right balance of adequate volume to rest and recovery.
I HATE that the resistance training community can be so tribal. I have been preaching to bodybuilders for years about the benefits of powerlifting, or Olympic lifting or kettlebells or even Crossfit style conditioning and many have been receptive. Learn from each other and achieve levels of fitness you simply could not have otherwise. Don’t brush off bodybuilding wisdom…it could be the missing factor in your program.