D&D has lots of forms of mystical bonds, a wizard's familiar is one example. The specifics of this form of mystical binding are not detailed any further in that sample. That represents a lack of information, not a rebuttal.

However, folklore and mythology, from which D&D draws the bulk of its material, does. And those sources are clear that dryads are the spirits of trees. Previous editions agree on this. Even the Kingdoms of Kalamar (an authorized D&D product) confirm - dryads are the spirits of their trees. So I am pretty sure we are clear on RAI.

I do realize that in strict RAW games, a lack of information is a rebuttal. But lots of things, like vampires, suffer a shocking lack of detail on any specifics as to their mythological roots, as presented in the game manuals. You are just expected to know that a vampire behaves in ways that are typical of vampires.

Anyway, not worth arguing over. My DM already takes the same point of view I do - dryads are the spirit of their trees (which is why he wouldn't let me transform their trunks into treants, darn it!).

So the basis of the question stands. In this instance, even if in none other, the premise stands and is sound.