Even supposing that it was sexual innuendo, that doesn't mean he was hitting on her. Straight men and women have conversations filled with sexual innuendo all the time.
Sexual harassment is harassment - behaviour intended to intimidate, disturb, offend, threaten someone - that uses sexuality as a vector. It's extraordinarily naive to assume sexual harassment isn't taking place if the aggressor's goal is not to elicit submission to sex itself.
Anyone have more insight?