The reason why humans behave morally acceptable, is because the have a desire to. What drives us might be that we would not want to experience the opposite happening to ourselves, but that might also only apply to the part of ethics that is covered in our justice system.

The ethical rules we restrict ourselves by in order to behave morally acceptable can be summarised to: "Do not do what another person would not want you to do." Obviously, this system leads to conflicts in many cases in which two individuals could each be affected negatively by two different approaches to an action [not in all, because while ethics do not dictate compromise, they do pretty much rate preventing damage higher than ensuring profit], but that is not the subject here.

For what reason would that not apply to strategy for sex?

And is this concept supposed to apply only when no harm is dealt outside of that sex-strategy-context? How far does this go? Are you supposed to be allowed to have sex with a person who you know is cheating their own partner - even though this clearly breaks the basic ethical rule?

If no, when does the rule apply? Does it only mean that you may use any assets you can offer to lure your seduction-targets? Because I would not see how any of that would be unethical - because as soon as you would do anything that would offend that person, you would already be outside the solely-sexual-context again.