Steve specifically said South African Leopards. Not regular leopards. I saw wild SA leopards in Cape Town in the big nature reserve down at the tip of SA. The climate there is similar to San Francisco. Cold and clammy much of the year. The wild torts there were walking around in the sun when temps were mid 50s and 20-30 mph winds. I was freezing even with a heavy jacket on.You are dead wrong on the leopards being out an active in 50-60 degree temps. In fact a larger sulcata could withstand those temps better then the smaller leopards.
As for night time, all tortoises should be housed inside a shed or night box at night to protect them from any animals that may prey on them while they are sleeping.
I've never tested the limits of what either type of leopard tort can handle. I've seen plenty of regular leopards get sick with cool nights, and never seen any of them get sick with 80 degree nights. I know people who let SA leopards get cooler in winter, and they seem to handle it fine. I keep mine warmer, but I know they'd be fine with cooler with temps.
SA leopards are definitely from a more temperate climate, while sulcatas come from a region that is always hot with no "cold" part to the year. A cold winter day in sulcata land might drop all the way to 88, but it would quickly return to warmer, more normal temps within a couple fo days. By contrast, there was a crew member working with us in SA that lived up in the mountains. He said it snows there and the local leopard tortoise population hibernates under the snow. I did not go verify this, but he seemed credible. He was a bit of a naturalist, and knew a lot about SA wildlife and flora. Point being: SA leopards can handle a SC winter much better than a sulcata. My male SA leopards do a self imposed anorexia in winter. They greatly reduce their food intake in spite of warm night box temps. Conversely, in summer, they eat more than any other tortoises on my ranch. One 40 pound male leopard eats more than a 90 pound sulcata in summer. The female SA leopards don't do this. They eat consistently all year long.