It is kind of an inside joke (not the best description, but close enough). People in the military know how shitty some of their gear is. Military grade used in marketing only makes people who don’t know think it is tough shit. Military folk know it means nothing.

Military grade means made by the lowest bidder.

King Gizzard & the Lizard Wizard

Edit: that is assuming too late as in “wish I would have been into this band in high school” and not “half the band has died or they are broken up”