Hey Amir - You’re understanding is exactly correct. Medium will pay you ONLY if you are part of their partner program.
My goal is not to get paid by Medium.

My goal is to build an audience of writers who love writing, but have no or little business experience. I believe 100% that I can help these writers make a living writing. So having the email address of these writers who voluntarily opt and say they are interested, is worth significantly more than what Medium pays.

Context:
I love writing, and have been a creative my whole life (I was a touring musician for a decade). I made almost no money from it, because I had no business knowledge at the time.
I’ve spent the last six years working in business and scaling companies (I’m currently the operations manager for Capitalism.com). I am in a unique position where I can take my current experience and knowledge and apply it to help people who are creatives, but don’t have that experience or knowledge, similar to where I was a decade ago.