I think the realities about feline descending abilities are somewhere between what @cazzie and @Coloma posted.
Most cats have difficulty climbing down a tree at first, because their claws are curved only for upward climbing. When they try to descend face-down, they can’t sink their claws into the bark.
However, I’d say at least some cats can eventually climb down a tree on their own.
I saw my indoor-outdoor cat, Katrina, learn how to descend from a tree in about 3 seconds. She also figured out to descend from the roof of my house. I didn’t see how long it took her, but my guess is less than a minute.
For a different example, it took my outdoor cat almost 2 days to find out how to get down from the same roof. I’ve never seen him up a tree.