I was told by a Dana technical rep that if the filter has a silicone antidrainback valve (you'll know right away since it's red) then it's got the T03 media in it.
So the newest 51522s should all have this T03 media.
The T03 media is listed as a "glass enhanced" media, so it's not fully fibreglass, but a blend. I have no idea what % of fibreglass is in there though.