I just want to make sure i understand what you are saying correctly, when you say "we try to get students away from all sorts of finger splitting combinations".
Do you mean you want students to use the same fingers on both hands?
As in all four on both levers, or index middle on both levers.
Or to do you mean that they should not split at all and use all four on both levers?
Wouldn't you agree that it's more important to be consistent and always use the same finger combination, and build muscle memory so your reflex will always be the same, rather than focus on which finger you use.
When we coach, we ask students to use all 4 fingers either on the grip or on the lever, on both sides. So you're either holding on to the grip with 4 fingers or have all 4 fingers on the lever.
I absolutely would agree that it's much more important to be consistent. I also believe that using 4 fingers on the brake lever on a sport bike is overkill and makes blipping the throttle that much harder.. which is why I always use index + middle on brake lever and ring and pinkie stay on the grip.
You have to remember that the "S" in MSF stands for "safety". Maybe it's coming from the fact that on some bikes, the only way to achieve maximum braking, 4 fingers have to be used. Maybe it's that when we teach those who've never ridden before, it's easier for them to separate braking from throttle, but using all 4 either on the grip or on the lever.. whatever the reason, it's definitely a good, safe way to go.