Nope, I am simply doing a basic copy (move once the + sign on the cursor is activated), and then the scale by -1. It’s a confidential project so I cannot share it, unfortunately, but I just reopened the file to confirm my impression. After the copy command it had the same name, no appended #X. Here’s the entity info of the component after the copy (I assure you it has the original component name): 
It won’t let me add another image to the post, but I’ll try another reply and hopefully upload the Entity info after the scaling by -1 (I assure you that it has appended #6 to the component name.)
Is it a dynamic component that you’re working with. Non-dynamic components won’t be made unique when one is modified with Scale and -1 even in SketchUp 2015.
There are several plugins that simplify the Mirror operation, though the native tools can of course be used instead.
I like TIG Mirror, from the SketchUcation Plugin Store.
Select object, use toolbar or shortcut (I use Shift+m for Mirror). pick point, line, or plane you want to mirror about, then you’re done.
DaveR, I don’t know. Is there an easy way to query it to find out? I made the component myself, but it’s possible that there were dynamic pieces of furniture inside the top-level component. I haven’t used the dynamic aspect of components to my knowledge.
BTW, if the dynamic component aspect is determined to be a factor, it would still be interesting that FLIP ALONG AXIS generates different results in some circumstances than SCALE -1. My guess is that many people, if not most, see these methods as indistinguishable.
I experienced this same problem of scaling -1 creating a unique component.
I was working with another person’s file.
There was a dynamic component included in the group I was scaling -1.
I deleted the dynamic component and the problem was resolved.