i’ve seen the bullet points from that article riffed in different ways, but i think that’s the most important part:

• They know you rang a phone sex line at 2:24 am and spoke for 18 minutes. But they don't know what you talked about.
• They know you called the suicide prevention hotline from the Golden Gate Bridge. But the topic of the call remains a secret.
• They know you got an email from an HIV testing service, then called your doctor, then visited an HIV support group website in the same hour. But they don't know what was in the email or what you talked about on the phone.
• They know you received an email from a digital rights activist group with the subject line “Let’s Tell Congress: Stop SESTA/FOSTA” and then called your elected representative immediately after. But the content of those communications remains safe from government intrusion.
• They know you called a gynecologist, spoke for a half hour, and then called the local abortion clinic’s number later that day.

I've wondered if they don't know the data. They can perfectly read the convo on your device, assign a category what you're talking about and keeping that category. They don't store, read, know the conversation, they only 'analyze' it. F.e. if you talk about planes they may assign a category travel and sell your profile to holiday companies?

I don't know about this, I'm just thinking that's how I'd do it if I ran an evil corp.

Does it though when they control both ends. It is encrypted between each end which I guess secures against things like a man in the middle attack from outside parties but their app encrypts it on one end and decrypts it on the other. I have a very hard time believing that they don't "read" your messages at some point in that process.