I think it is an illusion because as you approach the speed of light everything in your wide view contracts to the front of where you are going, so it would seem like you are moving back. Stop, and you now appear closer. It's probably why you do not see this effect on sci fi films, instead they show the ship moving forward by streaking the stars showing through the window, which is more intuitive for our brains to understand.

You're not controlling an FPS character walking, you're controlling the 'throttle' of how fast you're moving fwd or backward. Holding it down increases speed.

Forward means light is hitting your eyes faster, making it look like the distance the light had to cross is condensed, meaning it looks further away.

Moving backwards slights the light hitting your eyes, to the point where you're moving away from the light, so everything goes black.

What you are observing is relativistic aberration. W does make your velocity increase in the forward direction.