This claim is mostly true. From what I found when searching on Zillow and Redfin under their "property details" tab, the term "master bedroom" is nowhere to be found. For Redfin, bedrooms are already listed by number with no defining terms such as "guest" or "master" bedrooms. Zillow has changed the term to "primary bedroom," but that was just under some of the homes listed in Eugene. Some properties still use the word master bedroom.
CBS News published an article titled, "Some realtors are no longer using "master" to describe bedrooms and bathrooms," in June 2020. This article talks about how some groups are starting to stray away from the term, "master," as it can be seen as sexist and racist. It mentions how some platforms have elected to change the term to, "Primary Bedroom."
https://www.cbsnews.com/news/realtors-master-bedroom-bathroom-terminology/
All in all, it is true, that many online listing sites have elected to push a more neutral term like primary to describe the largest bedroom and bathroom in a home, but the use of the term still varies depending on the agent or listing of the home.