Even when it's the ten trillion dollar combined market cap of FAANG (or whatever we call them now)?
Because that's not open source. That's free labor suicide.
And they’re not really the worst one could think of, as FAANG thenselves contribute a lot to open source software.
The salaries of the people who work on those projects are paid by the revenue streams generated by the companies.
You'd need to provide and justify some alternative definition of what open source should be to make your final claim make any sense. As it stands, your claim "that's not open source" doesn't match the reality.
Its not like this is a loop hole. Not descriminating against anyone (including faang) is literally the point.
What the FSF calls "free software" and what OSI calls "open source" are essentially mechanisms for implementing such approaches in a capitalist context, in which the abstraction of "intellectual property" is enshrined in law.