I see little point in rinsing off the glass in most instances, and the higher you go the less I'd personally recommend it.
Think about what is happening when you clean WFP, you are rinsing constantly, there is a constant flow of clean water, and all the time you are agitating your brush the bristles are continually being cleaned.
Spotting is caused not by large, visible particles, but by particles small enough to be virtually dissolved in the water and then left behind when the water has evaporated.
A grain of sand will not cause spotting, neither will a piece of grit, or several pieces of grit for that matter, it's the dust on the grain of sand or grit that will cause the spotting.
If you do your job properly, there is little need to rinse OFF the glass, I guess that potentially a flocked vikan brush could cause problems, but I can't comment on them because I haven't personally used them.
There are certainly occasions when i will feel I need to rinse off the glass, but 95% of the time there is no need to do so. by doing so you are just using more water than you need to and taking more time than needed too.
Ian