What I mean is: some boolean flags are perfect for the real world phenomenon they are representing e.g. is_light_on makes you understand perfectly that when it is true the light is on and when it is false the light is off.
There are other cases in which if you didn’t write the code and you don’t read any additional documentation, everything is not clear just by looking at the variable name e.g. is_person_standing, when true it’s clear what that means but when false, is the person sitting? Lying? Kneeling?
I’m obviously not talking about cases in which there are more states, boolean would of course not be a good solution in those cases. I’m talking about programs in which there are only two states but it’s not obvious, without external knowledge, which ones they are.
I think I see what you mean, you have two states and kind of opposite but you usually name the variable after one of them, so you have to “guess” the other one. For instance you could have isRightHand, the opposite state being left hand, but from the variable name you can’t be sure if it could be “not right hand” as in right foot or something like that. Man it’s kind of difficult to come up with examples.