All of these smartwatches have something in common. They support Bluetooth Calling and, thus, are considered “Tethering Smartwatches” as opposed to “Standalone Smartwatches” that need a SIM card for calling.
Some of them are actually “Dual Mode” watches that can do either Bluetooth Calling or Standalone Calling. When you put in the number (or choose a contact) and initiate a call, the watch first asks if you want local (using watch SIM) or remote (using your phone) to complete the call.