lol what a crapload of bullshit. They could have just said "Hey, we are forced to use lame adi material, so even a human born alien will feature the always awful ditigrade legs and their crap alien resurrection/avp sounds. We're sorry folks. It's just those dumbf**ks at Fox all over again. We really wanted to portray the alien as It was in the first film, but they didn't allow us"
I think you really don't understand how anatomy works in relation to being in intimate constant interaction with it, over the potential span of hours.
You can't achieve this
Because the human leg can only provide you as far as it was evolved to provide, and that's not be an active sufficient hunter, or just because it "looks neat", to have a human being in a costume running around with a phallic head. It doesn't work, it's been proven it doesn't work, and Alien Isolation further proved it couldn't work, for their game. They had to make up for it in Alien with heavy lighting and cutting down the scenes with the Alien. In Aliens, they sped up and reversed film, and cut it in quick shots, not to give the illusion of, what? what? A man in a suit. They could have done it, I actually agree with you, but the end result would have looked exactly like behind the scenes footage, and what Ridley Scott and James Cameron wanted to avoid to begin with.