Research standards are higher now, specifically for subject matter off the main focus of the work (in this case, a fun game and not guns). The increased adoption and utility of the internet has made a huge difference in the cost:benefit ratio for getting tangential details right.
It was a lot harder to do research, even twenty years ago, when the internet was still in the early stages of wider use. As it was then "library, have bought the book or nowt." Google and the like, plus wikipedia (and wikis spawning from it) have made SO much easier, it's not even funny. So you do kind of have to give people writing 30, 40 years ago a bit of slack.
(Hell, I LITERALLY could not do the moderns-armour side of my day job without stuff like wiki, google image search and fansites of all stripes.)
Nowadays, though? There are ZERO excuses for being lazy about it.