This is a bug is iOS because of which you might receive notifications on Apple Watch for the Text Messages/SMS that are blocked by “SMS Spam Stopper”. (If the notifications are silenced on iPhone, the same should happen on an Apple Watch.) There is a workaround using which you could silence or turn off the notifications for Text Messages on an Apple Watch. You could do this form the “Watch” app on iPhone.
Please see the below tutorial video to know how to do this