Cold shocking is a tecnique used to stimulate pinning in cold weather species of mushrooms. It consists in dropping the temperature of the substrate, to simulate a natural drop in temperatures that would be a signal to fruit for these species.
Tropical species like P. Cubensis do not need to be cold shocked to induce pinning.
The reason many people think that Cubes actually need cold shocking is because when we soak cakes we do it in the fridge. The reason we do this isn't to cold shock the mycelium (even though it does have that effect) but to avoid the bacterial contaminations that the prolonged dunking could cause.
A quote from RogerRabbit in THIS THREAD
"As for cased bulk substrates, I ran several
experiments a few years ago where half the trays were placed in the
refrigerator for 24 hours, while the second half were left at room
temperature. Both sets of trays went to the fruiting chamber at the
same time. Every single tray that had been 'cold shocked' pinned two or
more days later than trays that had not been cold shocked. "