And yes, I am aware that the standard says this. My counter question to that is: How much client-liberty do I have to accept? Where do I draw the line? How much is too much liberty?
And the answer is: there is no answer. Wherever any system draws that line, it's an arbitrary decision; Except for one, which ensures the least surprise and maximum interoperability (aka. the point of a standard): to be "conservative", and simply demand the standard.