I hear you. But if his goal is to be a relatively competitive fighter, he probably shouldn't be worrying about hypertrophy currently - or even strength, for that matter.
Seems like you have done enough strength training to have developed some base of strength. If you want to be competitive in combat sports, you need to focus on your skill development as much as possible. So you should absolutely try to train 4 days a week.
Right now I am a bit on the heavy side to bulking and I plan to cut through MMA and work in at least 2 weight lifting sessions to make sure I maintain enough muscle
Probably not a bad idea. If you try this schedule and feel like you lack the work capacity to complete it, you might want to try lifting once a week for maintenance or something else.
Also, you might want to look into a strength training program that is not SS. What are your numbers? (squat, deadlift, bench)