Jose Manuel Jurado Diaz clears up the mystery:
Today, I worked on a service request that our customer asked about how SQL Server sorts the uniqueidentifier data type. We know that uniqueidentifier store globally unique identifiers (GUIDs). GUIDs are widely used for unique keys due to their extremely low probability of duplication. One common method to generate a GUID in SQL Server is by using the NEWID() function. However, the ordering of GUIDs, especially those generated by NEWID(), can appear non-intuitive. I would like to share my lessons learned how to determine the ordering method using uniqueidentifier and NEWID().
Yeah, things get pretty weird because x86-x64 processors (Intel and AMD both) are Little Endian, and only the fourth chunk of a GUID is Big Endian.