Different for the specific device (or chip) manufacturer (assuming clones will never have duplicate serial numbers either). But nothing stops manufacturers of different devices to have the same serial number scheme.
A true EUI is guaranteed to be unique, if everyone adheres to the rules. (That is: only use registered EUIs, like TTN purchased a block of EUIs.)
In theory, the serial number could even match someone else’s true EUI. (That’s why even converting a unique MAC address to an EUI64 by inserting 0xFFFE in the middle is no longer officially approved.) Using a random EUI, adhering to the rules of random EUIs, at least avoids collisions with purchased EUIs. Of course, chances are low that duplicate numbers both happen to be used for LoRaWAN. (And even more so: with TTN.)
The ranges shown in the examples, do not seem to be registered.
Encryption needs a secure random value. Serial numbers are far too predictable for that.