"though it now seems you're saying that they don't become gods until they are personified."
That is exactly what I believe - I phrased it badly first time around. You can revere and respect something, but that does not make it a god. Offerings can be made to a place. You can leave offerings for the pixies that look after a spring or the nymphs that live in it. One day one of these 'spirits' gets a name as top-nymph and becomes a god(dess).