He wasn't even faster then a bullet 😛
Neither was Krillin at base. By board rules, all active powers start in the off position, such as Green Lantern shields and such, while passive powers get to be on by default, since they're involuntary.
Which means Goku doesn't even start in a powered up base form, just a base base, guard completely open at the bell.
If it takes him a half second to power up at base, that's a half second he simply won't have.