It's more the time we're hit by mines but I did notice many NPC miners in RES deploy minefields (they're miners, so... well, they have mines LFMAO ) when we shoot at them and get caught by their own explosions.
I'd not be susprised to know that such 5secs arming timer has been stealthy introduced to counter an NPCs' AI failure...
The design of mines is a failure. They can hardly be used in any activities in the game and whatever they do, we mostly have a better choice.