I wouldn't know for certain if that measurement is accurate, but that's the gist of it ;p Maybe we'll have to buy cucumbers to test it out.
Physics says it is complete nonsense. If you put it in the fridge overnight, it would be frozen solid in the morning. Not only that, but cold of that nature is expensive to achieve.
Even without physics, if it were 20 lower in the middle, and they were stacked, as they are in the shops, the inside ones would all freeze and stick together.
hmmmm, just wondering if I am taking this too seriously? lol
It might have some truth when it is still on the plant as, although I suppose they are effectively cold blooded, their normal processes would perhaps have a cooling effect. For instance, the inside of a desert cactus would surely be cooler than the outside which often gets too hot to touch? I would imagine it is more likely that it is the refreshing nature as using slices on the eyes does have a cooling effect.