I can see the point, but I don't think it's a problem as long as the concept is well-defined.
It's only a matter of getting used to don't assume, for example, "open" and "closed" to be mutually exclusive.
There are other fields that don't have the privilege of this formal setting: I expect the concept of "species" to be very important in biology, but there isn't a clear definition of that (yet) [0].