String Theory,
I have just today called the phone number you provided and confirmed that the discs you received were Mac model specific OS install discs and not just OS X 10.5 retail discs made available as a retail replacement.
(Just as I suspected!!!!)
Also, I am confused and curious how you were able to obtain OS X 10.5 Leopard replacement discs as Apple only ships OS X replacement discs with the OS X version that was originally installed on the specific Mac model when it was shipped new.
This is why Apple asks you to supply the specific Mac serial number!
This is how they determine what OS X version the Mac originally was installed and shipped with.
No PowerMac G5 ever shipped with OS X 10.5 Leopard! None!
All PowerMac G5s shipped with some version of OS X 10.4 Tiger, originally.
So, your theories are all wet as to the reason why Apple sells these.
They are simply replacement system discs that normally come with older Macs out of the box! Period!
I needed to definitely confirm your info as I had been recommending this info, based on what you told me, to help out other Posters/Users who could get OS X 10.5 Leopard cheap instead of paying the expensive prices online and many of these Posters are coming back and telling me they can't just simply order a set of these discs as standard retail OS X 10.4 or 10.5 discs.
Apple is telling them OS X 10.5 is no longer available and hasn't been for quite some time.
(I, also, knew this!)
So, what you have there are system replacement discs. Plain and simple. Maybe the reason you got OS X 10.5 discs is that Apple may no longer have any type of OS X 10.4 Tiger discs available any longer.
I never, ever take the info of a brand new Poster at face value. Esspecially when I know better. I made the mistake of doing so this one time.
Nevermore....