I've got a '79 Fender Strat that's crazy heavy ash, and a 90s Vintage Reisssue that's feather light...
It depends on where the ash is grown, that is the tree itself and not geographically.
'Swamp ash', as the name suggests grows on the edge of swampy land where there's a high moisture content in the soil. This leads to it growing with a very open grain and therefore less density - wood is basically semi solid material.
The ash my '79 Strat was made from was grown high up the mountain, where the soil is relatively dry. It grows with a tighter grain and is significantly denser as a result.
Believe it or not, wood grows on trees, and the environment the specific tree grows in dictates it's characteristics, probably more than it's generic species... bit like people.