There is no way that a thing owned by Meta can read your messages but Meta can't. I especially don't believe it because Meta already shares data between WhatsApp and Facebook for marketing and advertising purposes (https://theconversation.com/why-meta-is-in-trouble-in-nigeri...) and has been fined for more money than any other company in the history of the GDPR for transferring European user data out of the jurisdiction of the GDPR (https://www.forbes.com/sites/siladityaray/2023/05/22/meta-fi...).
tldr - they say that they're not reading your messages. they also have a history of violating users' privacy and then lying about it. take it for what you will.