Sorry if I didn't make my concerns clear to you, my English is a bit rusty. Because Photos as an editing tool is so limited, I try to bypass it as much as possible. Unfortunately, Apple in its infinite wisdom makes photo file management for IOS photos very convoluted. Image Capture is a partial answer but sadly also "crippled"... you can import from an iPhone but you cannot delete the pictures once downloaded (this is an incomplete answer but time is money). This in turn is coupled to a rusty implementation of iCloud, which starts choking and asking for more money because the incremental (!!) backup has filled your pathetic allocation of memory.
Until recently, my workflow with pictures on the iPhone was to download them using ACDSee on Windows, but the newest IOS iterations now prevent this, which is why I am frustrated. (Even then, I was obliged to return to the Photos App to delete the originals, which I needed to do because my iphone memory is always nearly full).
So to answer your message point by point:
1) I am aware that some original images are not on the physical iPhone; but I am referring solely to pictures whose original files are most definitely on the machine in question.
2) Photos has some very good reasons for protecting the original files, but for my workflow I need to be able to copy those onto another storage medium
3) The Photos app does of course allow external editing, but my photo edition equipment is on a separate Windows machine and my edited files have no contact with the app. I realize full well that trying to put the edited files back in the labyrithine Photos file system would have dire side effects.
4) Importing with Image Capture, as I pointed out, does not allow deletion on the iphone.
5) And boy do I wish using Photos were optional. Apple makes it almost impossible to circumvent it.
Each of us has his own habits and areas of knowledge, and I appreciate your taking time to try to educate me, however as I often do commercial work as a photographer, and have something like 700,000 pictures on my Windows machine alone, reflecting the 60 years I have been taking pictures, plus the work I do in developing apps for IOS and Mac, I think I do not need to be accused of complete ignorance.