As far as I can see it there are several ways to track a mac system:
- Mac addresses of network interfaces (and I think bluetooth as well)
The hardware-uuid seems to depend on the used hardware of the mac. It seems to change if one exchange e.g. a graphics card:
It is possible for a system to lose its serial number so that it
will no longer appear either in System Profiler or the I/O Registry.
Repairing a system by swapping hardware components is one reason this
can happen. Apple does not document the specific details of how a
machine can lose its serial number. Once the serial number has been
lost there is no means to restore it to the machine.
Apple does not guarantee that all future systems will have a software-readable serial number.
Both of these cases illustrate why asset tracking software should always provide a way for a serial number to be entered manually.
As far as I can tell they mean the UUID when they say „serial number“.
The serial number of the system seems to be fix. I have no prove for this other than that it is used for registering your mac with Apple.
In theory Apple as well as developers are able to identify your installation based on your hardware. If you clone your system to new hardware there will be new UUIDs and serial numbers for the new installation.