What you posted is correct IF the Pacific location does NOT go on DST. If they do, then they would stay 3 hours behind NY. Your example specifically states it is comparing Pacific standard time. In other words, if both are on standard time, or both are on DST, then it is three hours. If only the Eastern location goes on DST and the Pacific one doesn’t, then it is 4 hours.
I think you might be mistaking the emphasis as mine when I just copied it from a time / date site. And "I guess this explains it" was about my mistake with daylight savings time, aka it depends on the time of year. It was not a criticism of anyone so please don't take it that way.