I don't think it true at all. I think some guys like to say hi and some guys like to say Hey. It means the same to me.
i dated this guy and if he said "hi" he didn't feel like talking. (this is text by the way, in person its easy to tell.) however, if he said "Hi. :)" he wanted to talk. boys suck. it just depends on the guy.
I'm pretty sure that hi just means hello.