Conditional Coverage when conditions are interdependent

Consider the following code:

public void isTeen(int age) {
return age > 10 && age < 20;
}

The return line has two conditionals, and thus has four possible states:

age = 5 : age > 10 = false : age < 20 = true
age = 15 : age > 10 = true : age < 20 = true
age = 25 : age > 10 = true : age < 20 = false

AND...

age = ?? : age > 10 = false : age < 20 = false

The problem is, there is no age where both conditions would evaluate to false. The best conditional coverage possible here therefore is 75% as there are only 3 possible paths that can be taken.

I'm however not sure if this is a problem or possibly a bug in Cobertura. It seems more that this is a special case that could be handled better when conditionals are interdependent. Perhaps this can be solved, perhaps not, but I'm reporting here as I did not see this specific problem before (there was another report that phrased the problem differently using 2 bools, but there was no relationship between them which I think why the report was marked invalid).