MwRYum
Major
I think the problem is system wide. not just PLAN but PLA and PLAAF. the materials involved might be part of it. Some of that stuff is kept close to home non Exported and non-license except to close allies. the bigh makers being European and American.
Also The PLA or perhaps China as a whole likes to make everything indigenous. It's possible they just don't have a maker in the PRC or one who makes to the Spec wanted.
Primary material for anti-flash gear is Nomex, the same type of flame-resistant materials found in fight-fighting gear.
Considering both the anti-flash gear and flame-resistant materials have been around for more than 50 years (DuPont first market Nomex in 1967), why'd China haven't come up with something of equivalent?