Why can Facebook Conversion API, instead of Pixel, overcome iOS 14 privacy policies?

They claimed that the Facebook Conversion API is the solution to overcoming iOS 14's privacy policies, however I still have two questions:

1. I understand that the Conversion API is sent from the server to Facebook, but the event must still be triggered from the client side, correct? So, if adblock can block all existing tracking domains, would the conversion API, like pixel, become obsolete?
2. If the event is sent from the server to Facebook, there is no way for the event to know the client's device information or anything else, so this information must be coming from the client, but iOS 14 has blocked those information access authority if the user selects "Not Allowed," so the conversion API should still be useless compared to pixel, right?

The events are sent from the client to a conversions api service on the client domain, so they’re not blocked by cross-domain privacy restrictions.

The service can then relay those events over to facebook, server to server.

client => fb.mydomain.com => facebook.com