Vagrant Lustoid 2

It is a simple matter of physics. And since we've not seen light follow different laws of physics in the show, then in an argument dealing with light we can only rely on what we know to be true here and apply it to DBZ, otherwise the whole argument is pointless. So don't say 'lolDBZphysicsnotrealphysics'.

Vegeta can track a Death beam because his mental and nervous capacities have sped up. This means that the electrochemical signals sent from his retina to his brain, and the subsequent processing and attaching of meaning to those signals, happens much faster than a regular human. However, his eyes still rely on the light hitting them to form the pattern on his retina so his mind can perceive it.

If he's passing things before the light from them hits his retinas, he cannot perceive them, no matter how fast his reflexes are, because he is physically not getting any signal. Think of it like an antenna system or something. Most people might have a CB radio, good for a few kilometers, but Vegeta might have a satellite boosted system that can get signals from halfway across the globe (likened to increased reflexive speed). However, if the signals are being prevented from hitting his antenna for whatever reason (a mountain, being in a lead-lined room, doesn't really matter), then it doesn't matter at all how good his antenna is, because he's not getting the signal. This is what happens when you surpass the speed of light. Your retinas aren't getting the signals required to perceive what's going on. The same applies to Gotenks.

And since this would be an impossible and foolhardy way to fight or even travel, clearly he doesn't move faster than the speed of light.