I have no clue personally
I've noticed that Saotome Sensei, with whom my dojo is most directly affiliated, seems to use what I'll call a "hybrid hand" that's more, or less open with the middle, ring and pink fingers held somewhat more closely together while the index finger and thumb are somewhat spread apart from the rest. I'm not sure if it's conscious, or more incidental, but it is interesting and certainly seems to work.
The key thing about Sensei's hands are how "alive" they are. It's not about some special way to hold them but while relaxed, they are energized. Many folks, in an attempt to be relaxed, lose this and have what I call dead hands. You can see when they are about to get grabbed, their fingers are curled lifeless... I think styles that have exaggerated finger splaying were merely trying to condition folks to avoid this. Saotome Sensei's emphasis has always been on feeling "natural". the way his hands appear is a direct result of that being how they are when they are relaxed but active, as if he were playing an instrument. For him sensitivity is crucial and tension is as bad as being too relaxed and de-energized.