Converting From "Save only the deepest term" to "Save term lineage"?

On my current site where I am using HS, alot of nodes have been created and HS/vocab terms have been added to them.

Due to new requirements, I now realize that I need to change my vocabulary/HS setting to "Save term lineage" rather than "Save only the deepest term".

I noticed that the transition from "lineage" to "deepest term" seems to work okay (after clearing the cache). But in my experience, if I want to convert a node's vocabulary from "save only deepest" to "save term lineage" it appears that I have to re-enter this information from scratch. (Otherwise, when editing the node, nothing shows up for the taxonomy. If I then switch back to "deepest term" and clear the cache, I can see the taxonomy information again, so it looks like it's not deleted when changing the settings).

So my question - Is it possible to convert my vocabulary to use "save term lineage" without manually changing every node? I figured I'd ask before going brute force...

Thanks.