https://www.cnet.com/news/facebook-is-still-tracking-you-after-you-deactivate-your-account/

As of January, I started deactivating my dummy account every time I used it, rather than just log out. I couldn't break up completely with Facebook because I needed it to sign up twice a week for a workshop.I thought the precautions would reduce how much data Facebook gathered about me. Turns out, I was wasting my time.

Even when your account is deactivated, the social network continues collecting data about your online activities. All that data gets sent back to Facebook and is tied to your account while it's in this state of limbo. It's as if you'd changed nothing.