Found while testing MC-248682. Very closely relates to MC-244190 - it appears to be effectively the same issue in that it was only resolved for entities and was not for pistons.

The bug

Fog starts to occlude moving pistons far earlier than it does normal blocks and entities, especially vertically - it appears to still use the spherical fog rather than the updated cylindrical fog.

How to reproduce

1. Connect pistons to a redstone clock
2. Travel far enough away from the pistons such that they're close to being obscured by fog, but not quite (low render distance recommended)

Expected results

The pistons would still fit in with the other blocks, being occluded by fog at the same rate.

Actual results

When in motion, the pistons appear almost completely fogged, even if the blocks around it are only fogged to a comparatively minor extent.