It's just a matter of opinion bro... maybe I'm not in the right place but I'm coaching 7-8yr olds. The video I posted is a simple drill for early arrives to the sport, some who have never thrown a ball. For me, having a 7/8yr old fumble around with a water bottle is only going to silliness. This is an open environment for everyone to share and learn... snarky comments like 'waste of time' doesn't benefit anyone. My hope is maybe folks will find the water bottle drill helpful and maybe some will find the one I posted helpful.
You are free to teach whatever you think serves your players best, and I agree, it is a matter of opinion. That said, there is a large contingent of DFP'ers - including people who have been around the game a long time (like grumpy ol' Greenmonsters) - who have a very strongly-held opinion that the throwing pattern taught by Austin Wasserman is best because it matches the throwing patterns of the best players in the world. Personally, I try to teach the skills young players will need going forward in the game, not just what will get them by right now.
I have been coaching my DD since she was 8yo, which included her very first 8U rec ball team. What I found was that 7-8yos will learn what you teach them. Teaching the water-bottle drill isn't any more complicated than what was in the video you posted. What I have also found is that teaching good fundamental movement patterns from the beginning means the players don't have to break down and re-learn those things later. Currently, as a coach of a 12U TB team, I see quite a few girls making the move from rec to travel with sub-par throwing patterns because that's the way they were taught early in their development. Getting those patterns to change is sometimes a difficult process because of deeply-rooted muscle memory. A poor throwing pattern can not only be limiting to their effectiveness on the field, but can lead to injury.
As for this forum being the right spot or not for you to learn more about the game, that's up to you. In my experience, the shared knowledge available on DFP is an extremely powerful learning tool, but will sometimes require us to challenge our own beliefs and opinions. When I was a new softball-parent and coach, nothing helped me learn more about the game, and how to be a better teacher to my DD and her teammates, than the knowledge I gained on DFP from people who have been down the road before me.