The distinction between chosen reciprocity and expected reciprocity is indeed one aspect of the concept, and they do indeed have generally different circumstances and motivation. I would add that chosen reciprocity has additional context here that also play a major role. Let make an example here.

Let say you are helping, for free, young adults/children to learn programming. You sacrifice time and energy for a good cause, and generally make the world a better place. No string attached, and no expectation for payment by those you help, a clear example of giving something away with no conditions or string attached.

Let now say that a for-profit tutoring company notice this and start to send their students to you. Instead of paying expensive teachers, they will use you as free labor and still demand payment from the parents. Does this change the context for your teaching? The parents, not knowing that you do this on your spare time for no pay, starts giving demands and expect you to behave as a paid employee, and do not recognize the sacrifice. Does it now mean something has changed, or are you still doing the exact same teaching to children as before?

I have seen multiple times when developers that release software under permissive licenses getting upset and stop developing when a for-profit company takes advantage of the fact that the license was permissive, breaking a social norm that has been created around the project. The permissive licenses only worked for those developers if everyone followed the social norm of reciprocity. How should such motivation be interpreted?