They super don't. And just as far as stuff "really" in-universe, the relative ship scales are a bit off, too. So stuff like the in-game rate of fire for a weapon really doesn't translate into its in-universe rate of fire at all for several different reasons, if that makes sense.
Just to clarify, because I see that my initial post seems to be confusing. I don't want the wording to be "realistic" or anything and the glock/LMG-not-LMG was more of an attempt at humor.
My point is more along the lines of:
Is the specification of "1200 rpm" in the description even needed?
Or could it just be rephrased to "Any weapon that employs chemical propellant to fire inert projectiles at
over 1200 rounds per minute a sufficiently high enough rate can be classified as a light ship-mounted machine gun"
Seeing how it not only conflicts with numbers readily available in game (which is where the joke about the LMG not being an LMG comes in), but with numbers in general being removed more and more from descriptions as updates progress.
Old numbers like the "45m killradius on the flak"
The "480mm-atropos torpedo"
The "two 120mm L/89 barrels of the hephaestos"
The "550mm-reaper"
The "1.8mm Schwarzschild radius Mjolnir"
and a bunch of others that I most likely missed.