Real Estate Agents and Builders to stop using the terms “master bedroom” and “master bathroom”

They're over thinking it, maybe to even get into the news. But, Primary bedrooom works too.

Aren't boys referred to as "master" before they're a "mister"?

I don't think the word is offensive, except maybe in a few contexts.

Yes, they are. In my wife's secretary are a box of cards leftover from when I was a little boy which refer to me as "master". I think they were sent out as thank you notes for 1st communion or something, but I sure as hell know from the time I was 10 that they were in bad taste. I may pull them out and have a conversation with my daughter to contextualize how ingrained racism is or, rather, was in the south when I was little.