I don't have a leather case (silicone here), but I'm guessing it has minimal / basic protection (vs cases that specifically pitch drop protection)
I do recall someone posting apples regulations for phone cases & I think there was a reference to protection / drops?? (Maybe I'm just imagining it, lol)
I think it would depend on where & how it feel. There have been those youtube case test & they all show different results.
I'm sure somewhere here with a leather case will have more info, but I've read on the boards here some people with leather cases had experienced drops & their phones weren't damaged......but I'm sure results vary.