UUIDs are 128 bits, or 16 bytes. They have infinitely many possible string representations. Those strings are not the value, they're a transformation of the value.
The strings are how HUMANS not machines interact with the UUID. When your java stacktrace spits out a log with an UUID it's going to spit out a STRING because it's written for you and not the computer.
When you take that UUID and go start sniffing around internal systems you're going to copy the UTF-8 string representation.
