It’s called laying low. It’s technically not even “pretending to be afk”, because simply not typing doesn’t by itself mean you are AFK for either faction, since if someone has nothing to say they probably aren’t going to say anything.
I know I make a point to speak a lot, but that’s to facilitate my own more aggressive playstyle. A different player will have a playstyle that doesn’t involve as much speaking, and thus they can be expected to go several phases without saying anything. This goes double for new players who genuinely don’t know what they should be saying in the first place.