If you look at it with a fine-tooth comb, the volume is okay.
On the surface, it’s seemingly insane, but when you go over it and look at how often a muscle group is hit directly or indirectly the number of work sets seem to fall into what current research indicates is the ideal range for hypertrophy. I’ve written a broad strokes comparison here,
Sometimes, it’s necessary to go deeper than the first impression when looking at splits and delve into the exercise selection. I’d argue that Gamma Bomb, on the surface, fools one in the same way that Dorian Yates’ split makes you believe that he only did back once a week, but really it was hit three days a week. Same thing with delts, seemingly there is one shoulder day but they are hit three days a week too.
I’ve actually been trying to think up a version of Yates that better align with your goals (trading some back work for front work) J but I don’t have the skill.