Not all the time probably, though in my experience, especially if it's not a flat share but a proper apartment, it's definitely closer to 100% (Berlin).
I guess the likelihood increases if you go through one of the newer screen-tenants-first-online-platforms or the building has hired a property management company. Going through newspaper-classifieds or owner-let apartments yielded 100% no Schufa for me in Munich + Berlin.
