I don't think it's so much about "draining your energy"... rather, the idea is that sex depletes your testosterone levels, and that can impact your game.
Go between a week or a month without sex or masturbation, and many aspects of performance are improved: attention span/attention to detail, strength, stamina, confidence, and some other areas.
How this, at all, effects the females when it comes to sex, no idea. But I do believe there have been some studies linking short-term abstinence to competitive improvement in numerous areas.
It's a whole different argument as to whether it SHOULD matter in the end, because if aren't trained well enough to begin with, then you haven't prepared properly. But sometimes that extra edge is all that matters, everyone is always after that small edge over the opponent. You can train and train, but so do they, so an edge is an edge regardless.