Cans of Swanson’s Natural Goodness chicken broth prominently state “Do Not Dilute” - as if doing so was to invite a dangerous chemical reaction or something - can there possibly be any reason for them saying so other than a wish to get you to use (buy) as much of it as possible?
(Obviously if you do so the flavor will be, well, diluted - but that works great for certain applications, say making polenta, where it gives a savory (but not overly chicken-y) result.)
I think they’re just telling you that the broth is 100% strength, not concentrated. If you want the natural chickeny goodness, you don’t add water. That is all.
Some broth is prepared so that you need to add a canful of water to get it to the right consistency. That’s just making it clear you don’t need to for that brand.