It is 100% different, because a fake spike is 1) not unsportsmanlike, and 2) doesn't cause immediate danger to a player, primarily the QB. With a fake slide, you are indicating that you are surrendering, placing your body in a somewhat vulnerable position, thus any further action from a defender is dangerous and illegal in the confines of the game.
A better comparison would be if one attempted to half signal a fair catch, or a vague gesture that could be interpreted as an attempt to signal fair catch.... only for the returner to run after the catch, claiming only pretending to signal a FC. Again, it's unsportsmanly, because the defense is agreeing not to hit the returner after he makes that gesture and catching the ball, in exchange for the returner agreeing not to try and advance the ball down the field. And it's dangerous because obviously the returner is in a defenseless position when trying to make the catch.
Word? Body angled? Like this?
On his way to make the slide? Leg on the verge of being tucked in?? Like this? Oh, wait, no you say he was FAR from being in that position.
Give me a break breh. Look how close his knee is to the ground. Look how on the verge his right leg is to being tucked in. You are deluded if you don't think this was close to a slide... he just happened to be athletic enough to stay up after getting his knee inches from the ground.