HD calling or 5.1 feature?

[bold1193]

So I recently got both 5.1 and HD calling on my Verizon Nexus 6 and I noticed a really cool feature! When I call someone, it will repeatedly blink "Dialing" until the person picks up and then it will say "Connected" with the usual call timer. (Before it and all phones that I know of would read "Connected" as soon as a dialing connection was established.
It is cool because I can tell now when the person actually answers the call! Anyone else notice this?

 

[Jaggrey]

I don't have the new software yet, but I noticed that change when I switched from Sprint to T-Mobile. I figured it was a GSM vs. CDMA thing. I guess it makes sense since I believe LTE is a GSM-based standard (but I could be wrong).