Two trucks with different HVAC responses

[Canuck57]

I purchased a 2015 Sierra SLT 2500 hd in August 2014 and picked up a Sierra 1500 sle sierra work truck in April 2015. Here's the issue when I use the hands free in the 2500hd the radio goes silent and the HVAC fan speed stays at whatever it was when I started to use it......now my 1500 reacts differently again engage the hands free and the radio goes quiet BUT the HVAC goes into low speed until I am done with the call. Are these two different systems, I would think the higher end 2500hd would have this low speed option built in as it is helpful and makes the call clearer (less background noise) which I then have to manually adjust the fan speed down,

Anyone know which truck is functioning correctly?