minor nitpick but the value of π is technically a parameter of the space you are operating in . which means it can have any arbitrary value as long as you are willing to operate in non euclidean spaces (and the space we live in is not euclidean though not to a measurable extent unless you are near a black hole)

but yeah in this context saying π is a constant is as correct as saying you cant take a square root out of a negative number .

edit : possibly better example is that a triangle’s angles sum to 180°