Either the phrasing is bad or it does not work for runes, since there is also the rune ring specifically increasing rune damage I do believe it is the second one.
I believe a bit of rephrasing from “Damage dealt increased” to “Weapon attack damage dealt increased” would fit better. I found a ring of broken promises (18% damage dealt increase) and against the same target with a bow dealt 15 damage each arrow with and without the ring equipped