Product and Software: This article applies to ArubaOS 3.4.x and later.
Yes, the Proxy-IGMP feature was implemented to allow users to continue their multicast session when a user roams to a foreign switch. The foreign switch joins the multicast group and sends the traffic to the user.
The Proxy-IGMP feature was designed for seamless multicast mobility by having the switch join the multicast group. Some topologies configure Proxy-IGMP, but have the user VLANs terminated on the controller. When we sniff the traffic on the uplink, we see the correct IGMP join messages and multicast traffic, but the clients never see the multicast stream.
The fix is to trunk up all of the user VLANs to the multicast router. Note that the feature was implemented for multicast mobility and not to replace the function of a multicast router.