So let's get this straight where does it say a seperate item needs to be drawn?
A wrist mounted weapon is attached to your wrist in the same way your hand is attached to your wrist or a selonians tail is attached to his torso or claws are attached to your hand.
Again it's fine if you want to houserule the item into that If that works for your group but let's not pretend it's anything but a houserule. Wrist mounted weapons are never sheathed or holstered just like your fists aren't thus no draw required because the whole point of the attachment is that you have these constantly at the ready (which again is supported by exactly what the description says).
The filed front sight is different for a few reasons, first being that such a weapon is still holsters and the front sight allows for a quicker draw since it won't catch ergo it needs QuickDraw to represent this. Note how it's not already in hand from that mod.
I mean your logic would dictate that if a player is walking around a hallway holding their gun at the ready to shoot what's around the corner that they then need to spend an action to draw the weapon even though it's already drawn, that makes no sense. The wrist mounted weapon is no different, it sits on your wrist and fires from that exact point making it already drawn thus it doesn't need quick draw because it is, as the description says, always at the ready.
Edited by Dark Bunny Lord