I disagree with this completely!
In any sparring, even MMA or UFC type there are 'rules' in real fights there are no rules. If you are skilled in grappling and you are in a tussle on the ground unlike in the ring/octagon there are no rules to say someone else wont start laying the boot in! You have to be prepared for the unexpected you just dont get that in sparring!
I love martial arts and will practice them until the day I die but they all have limitations unless you practice under adrenal stress and no rules!