surfline is a california based website and in calfornia (and basically everywhere else in the world) 2-3ft of swell is head high. 3ft of jersey swell at 7 seconds is a waist high wave. 3ft of california swell at 15 seconds is overhead. Take their reports with this in mind and you'll at least understand where their coming from.
I think surfline understands the difference between 7 and 15 second swell period. I doubt they are giving surf forecasts for new jersey in Hawaiian scale. They have an "ask the forecaster" blog that has pretty interesting stuff. The other day someone asked about east coast southern hemis and the answer was pretty informative.
either way, this site is better, and so is just looking at the raw data and making your own forecast.