If he ran out the back then he cannot be anything but out of bounds for a touchback.
If he lays there until an opposing player touches him its a touchback.
He didn't stand up and toss the ball to the ref, he didn't run in and out of the endzone.
To give up requires 1 of 3 things, a kneel down, a slide, or a refusal to get up while no one is around. A fair catch can also count in most circumstances.
The Texans player did none of that, he told his blockers what he was going to do but never gave the ref any reason to rule he'd given himself up. He walked a step forward and then just tossed the ball.