All wearing apparel sold in the US is required to have a manufactures statement of origin, cleaning instructions, and list of materials.
That is to protect the consumer from inappropriate materials and methods.
The enforcement is every bit as stringent as the return policy at the Swap Meet.
In your case, "NOMEX"might just mean it was not made in Mexico or with Mexican materials.
Simpson brand belts are made off shore (that is my nice) for example.
SFI is specified for a reason.