He is running HCG throughout so his recovery is going to be a breeze guys... his plumbing never completely went on hiatus. Recovery is going to be pretty easy on him. He is also controlling cortisol, so he has the hormones relatively in check.
As far as dropping volume and increasing intensity in PCT, this is to keep or maintain myofibrular muscle size, not the volume of the muscle itself. EI, the heavier loads with less volume stimulate the thickening of the muscle fiber, As to where adding volume to the workout does the exact same thing to the muscle, it adds volume, aka size but not via protein accrual. YOu also gain contractile tissue with high volume too, but only when volume is high enough that the fatigue of the fibers is causing failure to some of the fibers.
Certainly you will lose some "size" or volume after the cycle because you do not have super-physiological nutrient partitioning any longer so less glycogen will be stored in the muscle. Also with lower volume the muscle will decide it may not need as many mitochondria, and or fluid in the muscle cell. So you loose volume there, but as long as you do not lose the gained thickness in the actual muscle fiber then you have not lost your "gains".
Glycogen related LBM is EASY to regain, and a week or two at higher volumes with higher carbs will swell the muscle right back up to the old higher volume. So if looking at the big picture, lowering volume is often necessary to help with maintaining the CNS post cycle. Since that is often a must, or best case scenario, you want to accommodate that reduction in volume by lifting heavier to recruit & contract more muscle fibers more quckly with less drain on the CNS. Basically the more muscle fibers fatigue and fail due to intensity, the more are recruited with less actual workload due to the increased intensity. So you work less, but harder for the same effect on the contractile tissue without the drain on the CNS of high volume training. Obviously volume must also be dropped in order to maintain the higher intensity loads as well. They just go hand in hand in that aspect. High volume and high intensity is a recipe for CNS degradation!
Anyway the method is about preserving the size of the actual contractile tissue and not cell volume.
Remember there are two types of growth, one is sarcoplasmic, (mitochondria, intracellular fluid, glycogen storage and the like). This is volume driven, and the other is myofibular growth / contractile tissue growth which is driven by the intensity of the contraction needed to move the weight.
). You can actually feel your muscles crying for help during the workout. The way you tear those muscle apart with those slow reps and then drop sets..... mmmm