There was also the Leufken Technologies DFI that was introduced mid-late 2001, which was a direct-die cooling block that pointed a jet directly at the CPU die, albeit from a 45° angle.
There were direct-die cooling efforts from before that time as well, although I am unaware of any direct links.
While not "Enclosed DAI" it does still classify as core impingement.
The Silverprop Cyclone 1 was also out and about in
July 2001, and featured DAI.
Edit: Maze 2 was released prior to June 2001 though...