I didn't see the testimony, but I did read her book.

When most people think "targeted advertising", I think they are thinking about something like: this user is a middle-class woman between 18 and 25 who enjoys bicycles, so we'll show her ad X.

According to Wynn-Williams, Facebook/Meta is doing things like detecting when a user uploads, then immediately removes a photo--detecting that as a moment of emotional vulnerability (that is, the user was feeling self-conscious about their appearance), then bombarding them with ads in that moment for beauty products.

I think the former is 'obvious' to most people, but the latter probably isn't--probably because Meta and other advertising companies have put a lot of effort in to keep this on the down low--which is why Wynn-Williams is speaking about it publically.

(not accusing you of defending them BTW, just my 2¢ that this goes beyond what most people would consider obvious, imo)