For extra credit, here is the MERGE:

MERGE @Table T

USING (SELECT 5 AS col1, 1000 AS col2) AS V

ON T.col1 = V.col1

WHEN NOT MATCHED

THEN INSERT (col2)...

Nice question!

I was surprised that the final RAND() also returns a constant value after a previous call with a seed. It's in the Remarks in BOL, so I guess it's...

The result is undefined without an ORDER BY in the main query. Most likely the results will be sequential by ID.