While details are important we should not make the error to invent reasons why certain movements are important. Of course I can say spreading the pinky of the non hitting arm pre stretches the forearm for a more effective pull back, but that doesn't make it true
just because a lot of players do something it doesn't mean that it also has a function.
there is absolutely no proof for example that a federer like pronated take back is more effective than a DP like takeback. I'm not saying there is nothing to this but just because someone says so this doesn't mean that this movement must be beneficial.
I'm not saying that fed does random moves but often moves result from something further upstream. We should not lose the focus for the importan parts.