If you edit a text file, it actually just creates a new file because inserting text in the middle means all of the text after changes position. I'd still call that editing an existing file rather than creating a new file based on the previous one plus some edits. The second description might be more technically accurate but it's just unnecessary technical details because it's effectively the first description.

Even going back to the original use of edit, editors would mark up books or articles and then a new copy would need to be created with those edits. I'm having trouble thinking of any cases where edit truly means "change something in place without making a new copy of it with the changes included". I guess small edits with pencil or whiteout can sometimes work.