Isn't it used the same way in English? When you go to a therapist, you have a therapy session. When some musicians get together, they may have a jam session.

The technical meaning is very similar to the non-technical one.

I agree it's similar, though there's one difference: on many websites a session can have an arbitrary duration. If you log in to Google or Amazon once you can stay logged in on that device for months.

It seems inferrable, at least in broad strokes, from the other, non-technical meanings of the word. See for example "the court is now in session" or "I had a physical therapy session this morning".

Yeah, it probably is confusing to some. You might be able to skip the title entirely.

I'm not sure. Everyone learns it quite quickly after they are logged-out, but I don't think people know beforehand.

It's certainly not an issue for returning users. But I don't know how to improve it for first time visitors either ("logout" has the same problem).