if Google or Meta wants to join they should to us not us to them so if they break federation we should not care and continue implement our stuff
As I understood the article, the danger is that large actors like these are too important too ignore. Too many users, too much content to neglect. So while in theory you are obviously right, in reality there will be a temptation to cater to their needs, because it seems so worthwhile.
They have that ability, and always will have. They can create as many accounts as they like on as many instances as they like, or run as many instances as they like themselves, use incentivized individuals, or employees, or bots, or any combination of all of the above. No one can stop them, maybe even no one can spot them.
The only thing which is holding them back right now is lemmy/kbin still being too insignificant. If the network continues to grow, more and more big corps will see it as a market and an opportunity, and they will have plenty of ways to interact with it.