Other than answer the OP's question I decided not to get involved with the "discussion", until now.
A majority of top end machines have diabolos on them. There must be a reason why they're included. When the Babolat Sensor was released there was wonder why a diabolo wasn't included, and this is part of the reason it was included on the Star 5. At the French Open last year all the stringers were asked what they thought should be on their new machine, and a diabolo was one of the requirements that stringers wanted.
What a diabolo can also help with is the gripping point on the string. If you want to move the gripping point to a different point due it falling on a position where it could be at a critical point i.e. a bend, wrapping the string around the diabolo once or twice will help. Try and do that with a Sensor and it's a harder process to do as you'll have to let the tension head travel a bit before allowing to grip the string.
So, I believe the diabolo reduces the stress on the string, and the companies that make the machines seem to think that the inclusion of it is a good idea. And that is good for me.
Head IG Prestige MP; USRSA MRT, Wimbledon stringing team since '04; Babolat stringing team '10-'14. Twitter - @therqtstringer