That doesn't seem like a very sharp line (hah). "Abstract geometrical or statistical features like edges" have semantic meaning. An "edge" is just an area of the image with a high derivative, but as soon as you use that information to process it in some way, you are making some implicit assumption about what this statistical feature means - the boundary of an object, a discontinuity in depth, etc.
There is no dividing line between syntax and semantics - semantics is just syntax scaled. Godel proved it, LLMs exploit it.
If I run an unsharp mask filter I'm not making any decision about what individual edges mean. I might look at the result and decide to apply more or less sharpening, but that's still not "semantic editing", because the edit itself only sees derivatives.
There is no dividing line between syntax and semantics - semantics is just syntax scaled. Godel proved it, LLMs exploit it.