You give them WAY TOO MUCH credit. They just make this stuff up out of whole cloth and then refuse to admit it. They know that no other media outlet will take them to task for it. In fact, NPR will likely use the TIME article as a source for their reporting.
I think an earlier poster solved the mystery...airsoft apparently has a 600 round magazine....and since none of these lib outlets seem to retain firearms experts, they don’t know any better. Of course any attempt to correct them will be shouted down.