A woman facing you with open arms and legs and/or “looks” like she wants to give you a hug is a good indicator that she’s interested in you?
If you’re on a date with somebody then it usually is.
Somehow I doubt this. For one thing, women give hugs for many reasons having nothing to do with being romantically interested in someone.
You can tell if it’s the latter based on the context and the type of hug.
For another, she could be facing you just because she is talking with you. If I were having this conversation in real life with you, I’d probably be facing you. It doesn’t mean I am interested in you. Finally, she just may not feel like crossing her arms or legs at that time.
You took his explanation 100% literally and that’s why it isn’t making sense. Obviously someone isn’t interested in you just because they’re facing in your direction.