The difference is that in healt-related physical fitness sometimes different aspects of physical fitness get targeted and talked about compared to skill-related physical fitness. This means that when talking about skill-related physical fitness we can often talk about specific, skill-related aspects of physical fitness which can also differ quite substantially from general, health-related physical fitness. (imagine a bodybuilder having skill-specific physical fitness and someone who plays various sports as having a more health-related physical fitness).
