I think he meant that sometimes if a woman is into a man rather than treat him like a buddy she'll sort of put him in his place, in a flirtatious way- draw attention to the flirting etc. I also know of many people who are friendly and pleasant and then -it's friendship caught on fire. However it happens a person who wants to date another person will respond with enthusiasm and either say yes or no -I am busy that day but I'd love to reschedule. Or suggest a specific day they are free. The only sign that someone wants to date you is if the person either asks for a date planned in advance or accepts an invitation with enthusiasm. There are no signs otherwise - some people like flirting and feel chemistry but don't want to date the person, some people are friendly like that in general and don't want to date, etc. Many reasons.