Yes, that appears to be true. Males have red eyes, females have brown eyes. Males have more decorated shells. The back of the carapace on males flares out... that part of the female's shell usually does not flare out. So... looks like I met a fella and a lady. I bet they knew each other.
They spend more time in/near water than I would have guessed, but explains why I've found their shells when wade-fishing. I was also surprised to learn they eat a fair bit of meat.... snails, slugs, bugs, worms, fish, crayfish, frogs.... Aggressive hunters they must be! They can probably spend hours stalking a slug! Prior to the feast, they probably have a very intense stare-down! Nightmare fodder, for sure! 😜