In short
See Swell, Waves & Seas — wave height is significant wave height for that sea state.
This is explained in the swell / waves / seas article.
→ What's the difference between Swell, Waves & Seas?
Short version: forecast wave height is the significant wave height for the sea state being described (not every individual ripple), and swell vs wind-sea are called out separately when the product provides them.