I’m guessing that while the phone may support Wi-Fi calling, Telus has not taken the steps to activate the Blackberry Key2 on their network. The staff copying the specifications of the phone have not confirmed the network capability.
Just because the device is capable of using WiFi Calling, doesn't mean that it is capable of using WiFi Calling on the Telus network. Telus unfortunately uses a bastardized implementation that is different from stock Android. Because of this, updates for each device that actually work using the Telus (AT&T) implementation of WiFi Calling, need to be carrier specific. Also, Telus requires registration for your E911 address as well, not that this is your issue. Yes, the device does support WiFi Calling, but it doesn't currently support the implementation that Telus uses and might never.
Telus, like every other Canadian carrier, just copy and paste their specs without verifying them in relation to their network.
Telus unfortunately uses a bastardized implementation that is different from stock Android.
I often find Android how-to guides, but when I try to follow the steps, the options are different. If anyone ever finds an article on the changes Telus has made to its Android implementation, please let me know.