Footnote 2 is pretty clear to me that you can’t stack with status-based benefits: you get the higher of a) normal baggage allowance + 1 or b) baggage allowance with status/credit card.

So on a domestic US route with no baggage allowance, you would get one bag as a Gold (with or without the Main Plus bundle). Footnote 2 suggests that if you have a higher status that gives you 2 or 3 bags, you wouldn’t be brought down to only 1 by purchasing the Main Plus bundle (which should be obvious, but good that they state it explicitly I guess).

(I’m just going by reading the screenshot; no relevant experience.)