The main foundation of his argument is "spectators prefer shorter matches so making them longer loses viewers and the TOs lose money", but at no point does he give any reason to believe people would suddenly stop watching Smash matches if they had an extra stock.
In actuality, when it comes to online streams and such, a lot of people don't actively watch 100% of the tournament as it is. It's very easy to just keep it in another tab playing in the background. I do this a lot as it is, and it doesn't effect TOs since it counts as a view and as retention time.
And as far as local spectators go, well, if there is an entry fee for spectating, then once someone has paid to enter the venue, then you have the money there. If they leave early, that's their call, and it doesn't effect you.
While there still lies the possibility that less people would start attending over time, Omni didn't give me any reason to believe this would actually happen in his video, while also just completely discounting the opposite argument, which is just as possible in reality.
Throughout this post I have not stated my own opinion on what we should do, as I am not too sure to be honest (as a player I would prefer 3-stock since personally I get a lot of early KOs and matches are too short, but I realise there is more to it than that and the other elements are more complex), but I don't think this is one of Omni's best. He didn't give me any reason to agree with him ultimately.
I also disagree with how 3-stock "doesn't actually show the better player". No, it does. Mental stamina is a talent needed in any sport, and it has less presence in a two stock match. In a three stock match, it has more presence, along with the element of adaptation, and nothing is lost, in terms of the skills and talents that can shine.