I think it's all about the situation you're in.

Cus knew a thing or two about boxing and he'd have fighters who used his peak-a-bo style have a high guard - but not when they were punching or wanting to punch... it'd be once they'd worked in close to an opponent and thrown... they'd quickly retreat from a taller man with a high guard until they were out of range.

The objective during that phase of the style wasn't to punch, so it worked.