No, they're different things. A solo shower before or after any session is always free, as a courtesy to freshen up quickly or remove oil. The shower session is the shared experience: being washed, scrubbed, an experience, and looked after. One is a courtesy; the other is part of the treatment.
Together, we are in the shower together. When soaping and lathering you are usually away from running water, but never cold. I can position the water so that hot water is still on you at all times. It is a dedicated large modern shower and plenty of room for two people. There is time to also hug and be under the water at the same time too.
In combo sessions you can do the shower session whenever you want. Some do it on arrival as it helps them to warm up and relax in a familiar setting. Others do it at the end. Most do it at the end. If you wish to have a quick rinse after a massage and before a hugging session, that is fine, but you don't have to. You may prefer not to at all in your session. Entirely up to you.
Yes, you don't have to shower at all if you don't want to. Hair washing is optional, using soap is optional. But it's there as part of the session if you want it. If you do have wet hair and need some hair product or matte wax let me know.
No, but if you want to wash my back and chest I welcome it as it stops me getting all oily and pimply. And it feels nice.