You are incorrect on several parts of your assertion.
Mike Hart never lost to MSU during his 4 year career at Michigan. His “little brother” comment came after the 2007 game (Hart’s senior season) when Michigan scored 2TDs in the last 7 minutes to beat Michigan St 28-24.
Often overlooked in the history of the “little brother” comment was that it was an MSU player who -before that game- said MSU needed to stop playing like “little brother”. Hence, Hart’s comment after a reporter asked him after the ‘07 game if he thought MSU was “little brother”. “Yup” he said laughing and then continuing “if that’s what they call themselves then why shouldn’t I.” At that time, Michigan had won 6 in a row and 7 of 8, the loss being the “Spartan Bob” game that resulted in the B10 changing rules about the assignment of clock operations.
Michigan St.’s steak of victories in the series began the following year when Rich Rodriguez took over in A2.