This is definitely true, and there is an ongoing harmful perception that people who do sex work are seen as "unfaithful" partners as well (not even necessarily if they are currently involved in sex work, but that if someone has ever participated in sex work then they cannot be "faithful"). What "faithful" means is something that the people participating in the relationship decide on.
(Though honestly I kind of hate this "faithful" word and it's application to relationships in this way. It feels like such a shallow way of describing a romantic relationship).