The arguments about inclusive and exclusive definitions can go on for ever especially when one tries to make one point over another. In reference to rectangles and squares, weather a square can be defined as a "kind of rectangle" remains to be mathematically proven.
However, let's take the real fact:
Suppose a problem reads: The perimeter of a "rectangle" is 48 ft. Using whole numbers only, what is the dimensions that would give the greatest area?
If we are inclusive we can say that is a 12 ft by 12 ft = 144 sq ft. If we are exclusive we can say that is a 13 ft by 11 dt = 143 sq ft.
But what would the "correct" answer be in the real test-answer world?
Wouldn't you agree that since the problem stated "rectangle" the exclusive way would be the correct answer?