He may not mention in detail but he did mention to "coordinate hand with foot". The issue is, when you throw 5 fast punches in 1 second, do you truly have time to lift your foot and drop your foot 10 times within that 1 second? IMO, he addressed the power generation issue but he didn't address the speed issue (fast combo). Since WC guys like "chain punches", the "speed vs. power" issue is always an interested discussion subject.
IMO, "1 step 3 punches (such as chain punches)" and "1 step 1 punch (such as the boxing clip)" are complete different training. I don't believe Hendrick had ever addressed this issue either.