Hawaiian measurement started among local North Shore surfers as a way to describe waves modestly. Calling a 20-foot face "10-foot Hawaiian" was partly humility, partly code among locals that outside visitors wouldn’t read as fairly. Over time it calcified as the reporting convention for Hawaiian forecasts and some big-wave outlets.
Face height (also called "face scale" or "face-of-the-wave") is the direct trough-to-crest reading. It’s what Surfline, Magicseaweed, and most US mainland outlets default to.
NOAA NDBC buoys report neither Hawaiian nor face height. They report significant wave height (WVHT) — the average of the top third of wave heights in a 20-minute sample, measured trough-to-crest on the open ocean, in meters or feet. This is the deep-water measurement, before the wave stands up as it reaches shallow water at the break.
As a wave moves into shallow water and stands up to break, it grows taller — often to 1.3×–2× the deep-water WVHT, depending on bottom contour. So a buoy reading of "2m (6.5ft) @ 14s" often breaks as a 4–8ft face on a beach break and taller on a point or reef.
LazySurfer stores the raw NDBC WVHT reading and doesn’t try to convert between conventions. The ML Similarity Score compares apples-to-apples buoy readings against your own logged sessions, so as long as you log consistently (e.g., always mark sessions by face height or always by buoy reading), the model learns your personal scale.