In sparring I don't think it is a big deal, as long as everybody involved understands the point behind sparring. That, of course, has a lot to do with the skill and experience level of the boxers. It wouldn't make sense for two guys starting out, one a fly and the other a light heavy, to spar because they don't know how to box yet. They'd just be throwing punches, fighting.
I saw a guy, weighed 120 or so, and he'd spar everybody, any weight. But he was very accomplished , national #1 amateur in his weight class, and made sure everybody got good work.
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