Because the phone isn’t a thread device. There is thread information in the app.
The app is getting its information from the SmartThings cloud.
The SmartThings cloud is getting information about your thread device from a thread border router.
The thread border router has the thread logo.
Please read the community FAQ: it should clear up much of the confusion.
FAQ: What do I need to add a Matter device to the SmartThings app? Do I need a bridge router device?