As I remember, Shioda sensei in his book "Mastering AIkido" mentions to open up the fingers strongly in the opening pages of the book, part of kamae.
Check out this video of a yoshinkan practitioner.
He starts with fingers spread wide while addressing uke. As soon as the waza starts, I only saw his fingers spread once, at the end of an iriminage/tenchinage, actually twice the other in a swariwaza grab. I have no idea whether this is intentional on his part or not, but he is clearly only taking the spread finger direction of Shioda Sensei in a static setup pose, not during execution of technique. (I don't think you can say Joe Thambu Shihan's aikido is weak or ineffective IMO). So once again why?