I am not agree with you!)
Say you want draw a rosace
You have the circle
Start Arc from anyway on the circle
On = center of the circle
End = somewhere you want on the oposite side folowing on the circle and inspiration
due the design wished : can moving "end" on the circle is an help for the eyes!
So for me Arc 3 points by Start On End is a good thing :)

Maybe Michael can make 2 variantes: one for you, one for moi (me in french) :)

And can move these "3 points" a big help also! (before "validate" Arc function)
(idem for the "3 points" of a circle)