Its the only function that takes a GUID, however, and it only reports "static" properties, that is properties that will not change for this GUID. Which would kinda imply that a race/class/sex change will change your GUID ;)
Its used in the ChatFrame for Class Coloring, fwiw.
- the UnitGUID is definitly date/time based!!! (date/time of character creation! but there is no way to get this info. there is only an estimated date/time based on very large data and (server-based/WoW) experience).
Thats pretty inaccurate. They are numbered sequentially, so while one could argue that the date/time plays a role there, saying "date/time based" implies that the actual date and time take part in calculating the GUID, which is wrong. It doesn't matter if you create a character now, or in one hour. As long as no other player creates one in that time, the GUID will be the same.
I just know that my druid has a pretty low GUID (release day character), and i'm not tranfering it or anything, i want to keep it :p