Watching your rival undress before a sexfight is a common practice, one which generally serves two purposes.
For the woman who undresses, it is a chance to show your opponent the mistake they have made by challenging you, and the full measure of your sexual prowess.
For the watcher, it is an opportunity to not only measure your assets against theirs, but also a chance to form and forge a sound plan of attack. Which targets look most sensitive? How powerful are her thighs? Would engaging in a titfight be wise or foolish?
All questions that should be weighed, though one must be careful not to lose themselves in the minutia, and forget that ahead of them lies a battle which will be won by passion and prowess, not just plans and percentages.