you don't get it but it's important if a stat says "on this item" or global.

Then explain it so I do get it. Don't sit there and tell me I don't get it and then walk away. What kind of relationship are we in here?

What other item would it be on? It says it on a chest piece, what other item would it be on? Clearly only that chest piece would give me whatever the stat is. So you mean to tell me I could have an item NOT say "on this item" and it means it's on all items? Doesn't make sense.

Clearly if an item says +18% health, then its clearly only on that item. Never have I thought that an item having +18% health that it would be on ALL my items.

I feel there is a lot of added extra text in many parts of the game that they can remove. Might help with performance and make the file smaller, not that 16gigs is big at all.

The main difference, is that as you said. +x% on this item applies to the item you are wearing. +x% "Health" Does not apply to the other items, but would apply to your entire health pool.

In short form:

+X% on this item = increasing health/force shield/resistance on that item by that amount.

=X% "Health" = Increasing entire health pool by this amount.