Like a lot of things in this realm ("tantra" anyone), the words mean whatever the user wants them to mean. There is no universal meaning, nor are there any specific qualifications to offer services. Allen Silver, whom I've seen both for massage and SI sessions, is based in SF. As a guide, he has a very useful list of possible goals for an SI session on his website. It might give you some guidance in communicating with him, or other providers. If you don't want a generic experience, it's important to have a goal for the session (um, be realistic in what can transpire in an hour or two), and to communicate those goals as clearly as possible to the provider. I would say the first requirement for an effective provider is that he listen actively to the client's needs.
https://www.allensi.com/index.php/what