I have noticed this with almost all cats – certainly all my cats.

Why Cats Do the “Slow Blink” at Their Owners

I’ve used the slow blink thing as a way of communicating with them.  It seemed to show a message of trust, and, with strange cats, their tails usually stop twitching back and forth.  It’s nice to see this level of understanding with cats.  …  There are dog people, bird people, even reptile people – but I’ve always had cats – or, rather, they’ve always had me.