What is unique about the NCAA men's basketball tournament in 2023?
The tournament didn't include any top seeded teams in the final four, and included an exceedingly rare upset of a 16th seed over a 1 seed when Purdue lost.
Instruction: What is unique about the NCAA men's basketball tournament in 2023?
Context: 
Response: The tournament didn't include any top seeded teams in the final four, and included an exceedingly rare upset of a 16th seed over a 1 seed when Purdue lost.