Whether 250K or 500K pots will deliver for you really comes down to one's own personal/subjective tonal concept, in conjunction with the guitar in question.

If one likes things really bright, then 500K pots might be required, but BL's singles are hardly lacking in sparkle or treble response. And should one argue that 500K pots are required to bring any of Bill's pups to life, I would surely find the explanation for such argument in the wiring and/or the guitar itself and/or the rig, because it certainly is not a requirement/fault/feature/design flaw of the pickups themselves.

I see more requests to tame the treble response than I do to enhance it.

If L-500's with 500K pots are your ideal humbuckers, then you might require 500K pots for your singles, whereas if PAF tone is where your tonal concept of humbuckers lies, you will almost certainly require 250K pots for your singles.

If Barden's pups represent your ideal tonal concept, then you will almost certainly require 500K pots, otherwise, generally not. Same goes for anyone who has any significant hearing loss, because treble perception is the first to go.

If you have a dark rig, and/or run a long signal chain, and/or employ many pedals, you may well perceive the need for 500K pots.

Aide toi et le ciel taidera (Aid thyself and heaven will aid thee)