Source? the FAAMG plan with horizontally scaling the business into more markets is ultimately "benefit the consumer", so disallowing such expansion is effectively making products worse (for the majority; the minority customers unhappy with the new FAAMG-backed competing product do indeed suffer). If this policy is that narrow, they'll just slow acquisitions/product development and either start spinning off more companies or increasing VC spending, which doesn't move the needle besides detaching the company's name from their money.

What do you think Biden meant when he said "capitalism without competition isn't capitalism"?

Until we see some antitrust action that's an actual breakup and not 'locked down devices that aren't game consoles need to allow third party App Stores' we won't know the actual extent to which Biden is serious about doing anything to natural horizontal monopolies.