What is the time scale on this graph?
Who carried out this study?
It's absolute bull as Nat pointed out.
To simplify it, you have a brush, and a pair of arms, you need these arms to move the brush to cover the area of glass, whether the water is 000PPM, 000PPB, the whole area has to be covered then rinsed.
Now, the speed in which you cover this are is determined by YOUR arms, NOT the TDS of the water.
Say for example it's 10 seconds? On a monthly clean, Ionics claim what, 10% quicker with PPB cold?, so 9 seconds to cover that same piece of glass?
All I say is for them to PROVE it.
Come down, with one of your vans, go out with any one of my lads, and PROVE IT.
My lads won't be happy though, as they will finish early, so I can lay them less.