I think the description of metadata is good (my mental model is that a DAW operates on a stacked-up pile of operations to apply on top of the sources, and editing is all just adding/removing/modifying the parameters of those operations, which I think is equivalent to what you're saying), but the simple "doesn't change the contents of the actual file" standard I'm not sure is so useful. It would sweep up old Audacity and something like GIMP into the "nondestructive" pile just by virtue of each operating on a model where pre-existing source files get imported into the tool's native format and have to be exported back out.

Edit a WAV or JPEG with either of those and they'll dutifully not touch the source file (unless/until you tell them to export on top of it) despite internally operating directly on the data. (I think both have moved and are moving to offer more nondestructive modes of operation, but speaking of their legacy setups, anyway).