The legal problem & consequences for Facebook werent because of users who opted in to CA collection, the problem was getting your friend's data, who did not consent.
The legal problems for Facebook was mainly because they were an active party to the collection process, which could not have happened without that active participation.
This collection can happen manually, within the users’ regular and fully authorized use, without facebooks involvement, and in fact without any ability for them to figure out that it happens.
That it happens through a browser extension (which they may or may not be technically able to detect) should not change legality or legitimacy.
