Think about doing an escort quest where the NPC walks at 25% your speed and how irritating it is to have to keep waiting for them. Now imagine the NPC moves at %0.0025 or your speed instead. If he ever wants to travel with any companions, this might be more to protect his sanity than anything.
I don't read comics but I've hung out with enough comic nerds to pick up secondhand that the speed force and power cosmic are just straight bullshit. They do whatever. Think you found a problem or plot hole? Nah, magical powers specifically address that. Because magic.