Phone calls from non-cellular Apple Watch

Use your Apple Watch without your iPhone nearby - Apple Support

This text (bold) distinguishes cellular capabilities only as an additional path to make calls, and not as a restriction to making Wi-Fi calls:

Use your Apple Watch without your iPhone nearby

Learn what you can do with your Apple Watch when your iPhone isn't with you.

If your watch is connected to Wi-Fi or cellular

When your iPhone is off or out of range, your Apple Watch can use a Wi-Fi network to send and receive data. Your watch can also connect to a cellular network if it's a cellular model. And if you've set up an Apple Watch for a family member, they can use a cellular or Wi-Fi connection with their watch.

When your Apple Watch is connected to Wi-Fi, the Wi-Fi icon  appears in Control Center. When it's connected to cellular, the cellular icon  appears. Learn how to set up cellular.

A Wi-Fi or cellular connection lets your Apple Watch do the following things, even if your iPhone isn't with you…

The footnote (2) for making calls in the above article doesn’t distinguish Wi-Fi and cellular Watch models, only whether Wi-Fi calling is available and enabled.

I don’t have a Wi-Fi Watch to test this with.

Yes, if your carrier offers Wi-Fi calling and the iPhone is configured to use it: Make phone calls on Apple Watch - Apple Support

I have a GPS ONLY Series 4, and I just did some WiFi calling tests

I verified that my iPhone has WiFi Calling enabled. I'm on T-Mobile if that is an issue.

I verified that my iPhone Watch app says my Apple Watch has WiFi Calling enabled.

I powered off my iPhone. I tried to call my Wife. Failed

I turned off Bluetooth on my iPhone, so the only way the Apple Watch could talk to the iPhone was via WiFi. I called my Wife. Success!

So it seems that my GPS only Apple Watch cannot make its own WiFi Calling via T-Mobile unless it can actually communicate with the iPhone.

The only test I have not tried, is to separate my iPhone and Apple Watch so that the Apple Watch was on a WiFi network with access to the Internet, and the iPhone was Not on the same WiFi network. This test, should someone decide to do it, would involve the iPhone just on cellular, and the iPhone on someone else's WiFi network.

I am not going to do this test, as A) it is freezing a** cold outside at the moment, B) I do not have a suitable 2nd location for WiFi, and C) my home is in a T-Mobile dead zone, so I mostly only have WiFi calling at home. I would have to take my iPhone about a mile away to get cellular service for that part of the testing. Yes I could do this, but see item 'A' above 🥶

Well they are getting answered now 😁