The most appropriate comparison is DRIVER'S SUITS:
Driving suits that effectively cover the body from the neck to the
ankles and wrists, manufactured of fire resistant material, worn
with underwear of a fire resistant material. One piece suits are
highly recommended. All suits and underwear shall be made of the
following accepted fire resistant materials: Nomex, Kynol, FPT,
IWS (wool), Fiber glass, Firewear™, Durette, Fypro, PBI, Kevlar,
NASAFIL, or any suit carrying an SFI 3-2A/1 or higher certification
patch. Underwear of PROBAN is approved. The following specific
manufacturer(s) material combinations are also recognized: Simpson
Heat Shield, Leston Super Protex, FPT Linea Sport, Carbon X, and
Durette X-400. Underwear is not required with three-layer suits or
with suits carrying FIA standards of 8856-1986 or 8856-2000 or
SFI 3-2A/5 or higher (e.g., /10, /15, /20) Certification Patch . FIA
homologated driving suits and underwear are recommended.
(2006 GCR, emphasis mine)
In this case, it's probably appropriate to make the requirement based on materials and number of layers. Regardless, they didn't specify particular TPI burn-through test performance and did not align exclusively with one or a group of manufacturers, or one foundation.
With H&N systems, the best answer would be specific, impact head-load-reduction test results from an independent lab, since there are more than one way on the market to skin this particular cat.
K