I think it's best to stick with Tomo's suggestions at the beginning of the practice, not just because "Tomo said so". In my opinion, funk and rhythm guitar playing has important focus and foundations on the beat (and unity of sound). If we only use more of our forearm at the initial stages of our practice, it's much easier to focus on getting the beat and the sound right. It's simpler and gives less burden and variables to our brain to process.
In addition, parts of our hand aren't exactly isolated, in that they will work in tandem regardless of whether we want or not. It will be great to add more wrist force or angle for details and speed once we got the forearm section "right" (cross reference to bending where some people use more of their finger force but definitely they still have used some or little of their wrist force). I see in this way: precisely because Tomo stuck to his training routine for years, you can see that when he played Just Funky, his strumming is very consistent (the sound, the mute) and almost robotically accurate (in a good sense), but very rarely I see cover artists do the same, although they can sort of mimick the song generally. It's almost like martial arts practice - you train a million times for the few kicks and you develop something truely amazing; but if you don't set some of the foundations correct (such as beating the sandbag with the same simple jab for god knows how long), you don't truly advance and may be running circles at a stage.
Hugo