The answer is yes. In the sense that SQL Server will make it unique by appending 4-bytes to key. This makes sense given that clustered index is used for data addressing purposes (Correct?).
According to my research, it seems that SQL Server requires non-clustered indexes to be unique as well. And when non-unique column is used, SQL Server appends a 4-byte "uniquefier" value to make it unique. Is that correct?
Why does SQL Server require non-clustered index to use unique keys?