You can still gain mass using low repetitions, just like you can with higher ones Not everyone responds the same. It’s really the overall volume, number of exercises, etc. You honestly think he’s going to gain large amounts of weight from doing one lb exercise, ub push, ub pull, and pc exercise?
Also, the first 4 weeks are generally higher in repetitions with submax weights, often used in a general physical preparedness phase (GPP). In case you didn’t see he’s an absolute beginner.