OK, but in a "real" asset there is a limited supply of the thing being bought. You cannot buy an infinite amount of (e.g) houses, or corn, or pork bellies, because there isn't an infinite amount to sell. But I agree that you can invest an infinite amount of money in these things because as you buy up more, the price increases.
Derivatives remove the supply limits. Because, as you say, essentially derivatives are all about making bets rather than actually buying anything. If you want to bet a bajillion dollars in a derivative, the only thing limiting you is how many people want to bet against you. I get that this is similar to conventional supply/demand, but it's not the same.
The reason it's not the same is because there's no link to the actual production (aka what TFA is talking about) of the thing. You can make a bet that pork belly prices will go up or down regardless of how many actual pork bellies are being made. So capital flows get detached from actual production, which is where we came in.
And yes, I get that buying a stock is "making a bet" that the stock or share is going to increase in price. But that's only if you're speculating on the price. There are people (or at least there used to be) who buy a stock because they want the dividend. Or, perish the though, because they actually want the pork belly to make bacon with.