Yes sure. Code is logical stepwise. By including the "only if" it implies that other stuff is taken into account, which it isn't at that moment in code.
I mean, I don't need to extend the implications of an IF statement. It already does exactly what it says.
Anyway fuzzy logic does exist for people who want "sometimes if". It's useful in certain cases. I've only ever considered it in music production, where things very often get to the point of complexity where it makes a (sometimes) useful difference.
In normal parlance, "if and only if" rules out that something could also happen as a result of other circumstances. EG, if you fall out of a plane, you will lose your glasses. But there are other conditions that would lead to the same result.
In code, the alternative would be to have a different if statement that executes identical code. Or *cough* you could use a jump instruction to execute literally the same code.