First line on the page I linked:
Up to 4.5"of 2300° Ceramic Wool & Glass Blanket
Sturdy Gun Safes uses 2300 degree, 8 lb. density ceramic wool, and glass, blanket to line the fireproof safes. We feature 2 1/2" of ceramic insulator compressed to 2 1/4" for the right, left, back wall, and door jambs, to prevent the material from shaking downward. The top, and bottom will have 2.5" of ceramic and 2" of glass blanket. The door will have 2.5" of ceramic and 1" glass blanket.
It says "gun safe" but does it really matter what you put in it? UL will not test a safe lined with sheetrock which is why companies selling those RSC's have to say UL rated insulation. Something the link you provided also goes over. BTW that was a pretty well sourced link I will have to bookmark for later use.
Another thing to consider is distance from fire response time. I have thought of "remote" fire safe storage in a root cellar when I get land.
http://www.phoenixsafeusa.com/classification/datacare-2000-seriesI presume this is the one you are talking about but I don't see any TL / UL ratings listed. Do you happen to know this info?
If you already have a RSC or CSC you might find it best to put the smaller media safe inside that safe