There is a major difference between open ocean swell height and breaking wave height at the coast. Even at Mavericks at Pillar Point. The giant waves that are surfed here often break on swells that are between 15-25’ @ 15-18 second periods. When the open ocean swell nears the coast it begins to build in height as the deeper energy feels the friction from the ocean bottom. Eventually the wave jacks up in height and the top part is moving faster than the bottom and the wave breaks and people can surf it.
For example, last month I was surfing in Nicaragua and the open ocean swell was 6’ @ 18 seconds but the wave face at some of the bigger breaks was closer to 12’.
My dad was stationed in Japan in the 1950s when I was a little kid. To join him, my mom and I sailed from Seattle to Yokohama, two weeks aboard an MSTS ship.
I do recall seeing some massive Pacific swells, some seemingly higher than the top mast.