It wasn't in the manga?
My bad then. Could have sworn I had read it.
Edit: Just checked, and yeah it's not there.
Just as a thing as this spirals onwards, lightning saga Val of the "negate instant death effects as speed force lightning channels them into me" is basically the same dude as pre crisis Val, plucked supposedly from the very moment of his death. It's not as though he underperformed to that standard.
Plus the Johns Legion tends to ignore some stuff that happened before the first Legion reboot anyway.
There is a difference between travel and reaction speed in that for example, Thor can fly across a galaxy in a shot period of time, but doesn't have reflexes to match. If Karate Kid can move his arms and legs in such a way that he can juggle a PC Kryptonian, what stops him from moving them at the same speed and taking 30 some steps in the direction of Bills?
As has already been posted, Val shows travel speed more than human when not fighting, as he outraced a forming earthquake in order to stomp it away. He even had to flip down the side of a building holding a bystander before getting the chance to start running. FTL speed, no. Is it proof that Val doesn't need to be directly fighting with someone or dodging something directly to be better than CBPH? Yes.
And as has been pointed out to you, it is still not fast enough to even effect someone who is MFTL.