This sounds like a completely normal customer service experience to me, it is the only kind I have had for at least the last couple years or more. Hey did they at least speak English? that is a plus now as well. I had an almost identical experience with Comcast a month ago.
You are absolutely correct. People building dedicated home theaters often use sand filling the front stage, the area where the screen, front speakers, center speakers and often sub woofer are for the reason you mention. Others use packed fiberglass.