Maybe the developer added Save a Copy As because the others don't work. I'm just joking because I can't explain it. If it was working properly choosing Save or Save As should cause the window to refresh and the saved title to appear, whereas choosing Save a Copy as creates a saved file that is not open in CDSD. It is an extra copy but not the one you're seeing and working on.
I hadn't noticed the saving of the different extensions. They are the same file type but I believe Windows used to only recognize three-character extensions.
It does seem that the save, save as and save a copy as have different attributes. The reason/reasons are unknown to me. I am glad that the save a copy as does work as one would expect.
Here is a difference I have found:
I have Toast installed on my PM G4, PM G5 and my MBP.
If I create one track, do a save as, name the file on either my PM G4 or G5, it will save the file as a CDSD file with the CDSD icon. Of course the first save as makes the one track disappear and then I must actually create the tracks I want and do whatever editing I need to do. Then do the save and it works. But to me that's like opening Word, have to type one sentence, do a save as, name the document, the sentence disappears, then type what I really want and to a save to save the document as its suppose to.
If I create one track, do a save as, name the file, on my MBP, it has the standard audio icon and not the CDSD icon. I don't understand that, but that's what happens. Of course the first save as makes the one track disappear as on the PM's, but the file has the standard audio icon and not the CDSD icon.
Now, if a do a save a copy as on either the PM machines or my MBP, it works as it should. All icon's are standard audio icons.
So to me there is a bug in the save and save as routines on a PM (PPC) that is not occurring on my MBP. I do not know why, but it happens each time. Also, the save a copy as works on both platforms.
So I have gotten to the point that I just do a save a copy as all the time and have given up on messing with the save or save as commands.
For me the issue of save/save as has been in CDSD for a long time.
I am using 10.5.8 on all machines.