DAX traffic playing through All PC's on my LAN with SmartSDR loaded

This may be by design that DAX works this way.  Here is what I am experiencing.

I have SmartSDR (plus DAX & S-CAT) installed on my 27" iMac (Win-7 running on Parallels 9) running physically next to my 6300.  I have two other laptops in the home, both have SmartSDR, DAX and S-CAT installed so that I can do digital work elsewhere in the house.  Time to time, I'll enable the monitor ("Listen to this Device" check box) function on the "DAX Audio RX1" so that I can hear the PSK tones or even other mode sounds remotely.   All working fine.

Here is what I have observed and found interesting.  When SmartSDR is not running on either of the laptops (DAX still is running in the back ground.)  Should I start up SmartSDR on my iMac down in the Shack, the receive audio plays through the other two laptops even though the SmartSDR client is not running on either of these computers (because I have left the "Listen to this device" enabled.)  If I shut down all instances of PowerSDR but DAX still running on all PC's, the audio stream cease.   

My assumption is that this is the nature of a audio panel codec designed to receive audio via UDP packets.  Is this functionality normal and by design?