According to
http://www.onestopknifeshop.com/store/550.html, the military specification in question is MIL-C-5040H.
I understand that the cord should have two numbers (e.g. 550/220 - though I don't recall offhand if the second number is correct.) The first number is the breaking strength, the second number is the Safe Working Load (SWL). I'm going by memory and I'm sure someone more knowledgeable will correct me.
Basically, if it's dyed Olive Drab and meets the military requirements for Olive Drab colouring, then there is no actual falsity in advertising it as "milspec" as long as they don't specify *which* military specification it meets. Local laws may vary, of course, but I suspect that the word "milspec" may be one of those advertising catchphrases that actually has no meaning in law. It's like advertising something as "extremely tasty" - how could you possibly prove it wasn't?
I work in the defense industry, and there are "milspecs" for EVERYTHING! I can well believe that an unscrupulous retailer would market a product that meets an utterly useless military spec (such as the colour of OD dye used) and market it as "Milspec" paracord.
Can anyone confirm whether MIL-C-5040H is, in fact, the relevant mil spec (i.e. with regard to breaking strength)?