This strikes me as a pretty good example of what goes wrong when Rosen tries to force-fit his ideologues-pragmatists view of conservative jurisprudence where it really doesn't work.
Here, he arbitrarily labels "free-market conservatives" as the "pragmatists" while "states-rights conservatives" are the "ideologues." He offers no justification for those labels, and, indeed, you could just as easily reverse the labels: After all, Justice Holmes famously criticized free-market ideologues on the early-20th-century court , and Justice Brandeis' description of the role of states as our Republic's "laborator[ies]" was, of course, a pragmatic one.
Ironically, Rosen's own error on this point likely is rooted in ... his ideology. So devoted to his view of Scalia and Thomas, he allowed this sort of error to creep into his analysis.