in vanilla Xcom TFTD (which I played the most) I often noticed aliens throwing a grenade then taking a snap shot, and those weapons have higher TU costs . . . and then walk around a little
So they are not getting charged for Priming the grenade, only throwing it.
Maybe they have this little implant in their arm that auto-primes their grenades when they throw them eh? Too bad the xcom researchers never found it or the electronic receiver in their grenades that allowed them to be remotely activated in flight.
>>> reasoning ,the aliens never prime their grenades in advance, otherwise there would have been cases where you shoot one and the grenades he drops explode. Nevar happened in the history of gameplay.
(in other news, one can throw a grenade underwater up to a hundred yards, but in doom flynn taggart can carry every weapon in his arsenal too. thats games man)