"Intrigued by Garfield's reaction, Roosevelt finished reading the novel and invited the author to the White House during the first week in April. Although he proceeded to disparage the socialist diatribe tacked on to the conclusion, Roosevelt assured Sinclair that "all this has nothing to do with the fact that the specific evils you point out shall, if their existence be proved, and if I have power, be eradicated." By the time Sinclair arrived for lunch on April 4, a Department of Agriculture investigator was en route to the stockyards with an order from the White House to evaluate the novelist's charges. Sending a representative of the very agency that had failed properly to inspect the plants, Sinclair objected, "was like asking a burglar to determine his own guilt." His objections prompted Roosevelt to dispatch two additional investigators with no official ties to the department. He chose two well-respected men: Commissioner of Labor Charles P. Neill and Assistant Secretary of the Treasury James Bronson Reynolds."
I appreciate you citing the source, but that doesn't seem to back up the statement "he commissioned it and didn't like the result". He commissioned it, was advised of a potential conflict of interest, and dispatched a different set of investigators.