one comment: we can expect to see a difference when using "Edit in Photoshop", vs when using a named external editing preset from the Edit In... menu.
We may choose to use a preset in order to control the bitdepth, colourspace or filetype image-by-image; or when there are multiple editor programs in place.
In the former scenario, LR has told PS to open a file in memory and if this is not saved, LR makes no new image version. I am surprised that LR is "watching" to see where PS saves it aside from the default location and name - I was not aware that this channel of communication is available - but perhaps, this is just a question of a brand new file appearing at path B instead of at path A. So there is still only one file.
In the other case of using an external editing preset, I gather that LR will have already made a workfile on disk before PS opens, and then PS is passed the fixed location of that. So in this case a further "save as" by Photoshop will cause a separate file to exist - over and above the one which LR knows PS has opened. Even if PS is simply closed without saving changes, the image file in question is still present on disk, and also appears in LR unless/until removed.
