Is there an official name for those kinds of long paths in a single namespace? I found UNC, but it seems to apply only to the network variety.
https://en.wikipedia.org/wiki/Path_(computing)#Uniform_Namin...
https://en.wikipedia.org/wiki/Path_(computing)#Uniform_Namin...
The closest I can find is "To specify an extended-length path, use the "\\?\" prefix." (from https://msdn.microsoft.com/en-us/library/windows/desktop/aa3...).
So maybe it is the "extended-length path prefix".