If his method actively looks for increase/decrease of volume on following bars (which it does) then this type of presentation (again, an option in the charting platform) makes a lot of sense.
The logic is sound in terms of accentuating a phenomenon, however the varying height of a volume histogram provides that information. Adding color to the histogram reinforces a particular data point at the expense of another. Volume is either incr or decr. The exception is when it is the same, which requires a context to determine if it's more like incr or more like decr.
Yes, the price pane contains that info, and when someone's workspace is with the HRE, efficiency is key.