Yes you are correct, so the point to take from your quote is: "Specifically, a contract or agreement, whether express or implied, for a specific sexual service...". Even if everyone entering a massage parlour didn't specifically say, hey I'll give you $80 for a handjob, it can be proven that when they paid and later recieved a sexual service, they entered into an implied contract of service. Basically if pretty much everyone who enters a massage parlour receives a handjob and pays, there is an expectation of a sexual service to be rendered in exchange for money.