I don't get splits where the trainee hits a muscle group just once a week. Just not enough frequency. Smashing a muscle from all angles for 12-20 sets and then leaving it to next week? Obviously it differs from person to person and making sure the big rocks for adaptation are in place - sleep, nutrition, (supplementation ), etc but the accepted window for super compensation is 48-72 hours or 2-3 days after the muscle group has been worked. So completing those sets over the week in a 3x full body, or 1x LB : 1x UB : 1x FB, or 2x LB, 2x UB split will most likely be more beneficial to progress.Funny how things come round again.
Old timers were basically full body 3x week, then "once a week" splits became popular, and nowadays higher frequency is making a resurgence.