I recall at least with one person whose whole enclosure was 65-72 at night.
All my gecko enclosures are at room temperature for about 8 hours at night. In summer it's whatever the temperature is, I don't have A/C. It could be 70°F, could be 80°F+. In winter the furnace is set to 64°F, that's what all the geckos live with. The UTHs go off at 8PM, (back on at 8AM), the enclosures have pretty much cooled to room temperature by 10PM.
All species I keep, Rhacs, leopards, AFT, frog-eyes, and more, get cooled at night, some have been living it for around 20 years.
In the case of wild leopards, they get cooled at night, not just down a few degrees from 90°F. They go out to eat, mate, fight intruders, whatever they do when awake. They do all this when it's cooler, and with a full stomach. They might be up and about all night, or just a few hours, but come dawn they drag their filled bellies back home. They don't get properly warmed up until a few hours later when the temperature has risen enough to warm the burrow. Then they thermoregulate as needed. Digestion doesn't really get started until they warm up again. They only have a few hours at optimum temperatures so it could take more than a day to digest their food, another reason for not eating every day.
Even if they did head back to the burrow immediately after eating, they wouldn't find it warmed to 90°F or so, they'd still have to wait for the sun to come back the next day to get "optimum digestion temperatures".
Digestion does need heat, but that doesn't mean they can't be roaming around at night with a full tummy because it's cooled down.
Plenty of people who have not been properly educated at first have allowed their enclosures to drop below 70f. The results at times were not very pretty, URI, undigested food, poor appetite, ect..
Night drops to 70°F with proper day temperatures won't cause URI, poor appetite or undigested food. If it was that easy to get them sick they would have been extinct aeons ago. Poor health (e.g. parasites, infection) or husbandry would be my guess, the lower temperatures just amplify the problems.