Everyone always thinks avoiding a question means the answer is the opposite of what you want to hear.
However, it's pretty hard to interpret any sort of in game action as chokeslamming an alien unless the marine was infact choking slamming an alien. That's some pretty obvious stuff that's not really left to interpretation.
And well, yes... it is pretty unbelievable. Not only are we talking about a marine carrying all of his equipment and picking up an alien with one hand (the gun being in the other hand), We're talking about picking up a creature with one hand that has a tail that can drive straight through or puncture your forehead with a phallic symbol and tear you to pieces.
Would a 200 lb marine be able to pick up a cheetah by the neck with one arm and live to tell the tale? Highly doubtful. And cheetahs don't really compare to aliens.