This is totally untrue IME of modern mass timber buildings. The sound isolation is excellent.
I lived in a 6 story building in Santa Monica. I disagree wholeheartedly.
Given that Santa Monica is in the USA, my suspicion is that it's wood frame rather than mass timber as deployed elsewhere, with thick heavily insulated flooring, see e.g. https://www.youtube.com/watch?v=bZGuSC7KNvM