We've known this for a while Ser. I know because my mother literally gets Facebook adverts on things that were mentioned in WhatsApp text messages.
Discussion
Definitely this and have seen it myself, Meta will say it's advertising algorithms scanning for key words and not humans reading your conversations but that's not the point, if a backdoor or access exists and is built in then it can be used later for purposes other than advertising but hey-ho Larry Ellison says we'll all be on our best behaviour when everything we say or do is being monitored.