Which article are you referring to? The ones posted recently on site or one specifically on German Volume Training? 3 to 4 days should be possible for GVT.
I've done a program based on GVT, 3 supersets, 3 day splits (push/pull, legs, arms), Moving from A1/A2 to B1/B2 when weight drops below 80% or reps drop below 8 (10 rep sets), likewise for B1/B2 to C1/C2. 4 days a week was not an issue. It depends a lot on how you respond to volume as well.