It applies in two cases: when there is an expectation of privacy as you say AND ALSO when nudity/explicit sexual behavior is recorded for a sexual purpose.I'm not a lawyer but I did sleep at a Holiday Inn last night.
I think this law only applies where there is an expectation of privacy. It doesn't apply when you are doing the nasty on a public beach or on a public park bench.
One of the elements is surreptitious recording so if you are openly recording people that's not the same.