No mine does not need to have a cell signal. In fact is has yet connect to the carriers network. Again I know because the device is still grayed out when I check my account. Once it connects it will self-identify and will show up as an Apple Watch.
The feature just has to be enabled to allow for you Watch to register with your carrier's network. That means the eSIM is on and it can provide the information needed to connect to your carrier to allow Wi-Fi calling to work.
As a test, take the SIM out of your iPhone and try to make a Wi-Fi call, it will not work. The LTE on the Watch works the same exact way!
Put the SIM back in your iPhone and disable cellular and then make a Wi-Fi call. The only difference that I found is that the eSIM is not powered if you have the Cellular option turned off. This Watch really wants to save power.
Dave
The feature just has to be enabled to allow for you Watch to register with your carrier's network. That means the eSIM is on and it can provide the information needed to connect to your carrier to allow Wi-Fi calling to work.
As a test, take the SIM out of your iPhone and try to make a Wi-Fi call, it will not work. The LTE on the Watch works the same exact way!
Put the SIM back in your iPhone and disable cellular and then make a Wi-Fi call. The only difference that I found is that the eSIM is not powered if you have the Cellular option turned off. This Watch really wants to save power.
Dave