It is worth noting that the TSSI isn't the only one around any more, though - nor is the strictly quantitative interpretation of value theory. The TSSI was constructed as an interpretation to solve the transformation problem, but there's Dumenil's New Interpretation now and Fred Moseley's Macro-Monetary Interpretation. It is not surprising that Freeman would make such a concession as an economist rather than as a philosopher, where Marxian value-form theory flourished in Germany and Japan during the 70s and 80s and still to this day.