Legal scholars and historians frequently make sweeping conclusions about the Supreme Court and its individual Justices based on votes in particular cases. The problem is that until relatively recently, the norms on the Supreme Court discouraged dissent, and the Justices may at certain times have had additional reasons beyond those norms for joining a majority opinion they disagreed with.
I've been working on chapter 4 of my book-in-progress, Rehabilitating Lochner. This chapter deals with protective labor laws for women, and liberty of contract challenges to such laws. In 1923, the Supreme Court invalidated a minimum wage for women in a 5-4 vote (Adkins v. Children's Hospital), but a year later the Court unanimously upheld a ban on night work by women (Radice v. New York).
The apparent inconsistency in these cases has led scholars to explain the discrepancy in a variety of ways, none of them complimentary to the Justices. One obvious but generally overlooked possible explanation is that in the night work case, the Court felt bound by a 1908 precedent (Muller v. Oregon) upholding a maximum hours law for women on the grounds that women are physically weaker than men, a rationale that simply did not apply to the minimum wage law.
But I just stumbled across something another interesting explanation. According to Felix Frankfurter's notes of a conversation he had with Justice Louis Brandeis, Brandeis told him that Radice almost came out the other way, but Justice George Sutherland, who had written the Adkins opinion, switched his vote at the last minute after agonizing over the case for some time. The other Justices still thought the night work ban unconstitutional, but with the Supreme Court under attack (most notably by future Progressive Party candidate Robert LaFollette and Senator William Borah) for issuing controversial 5-4 opinions, and with Sutherland having jumped ship, the other Justices chose not to issue a dissent.
Assuming that Frankfurter's notes accurately describe what went on, instead of a 5-3 vote (with Brandeis recused) split on women's protective laws turning a year later into a nine to zero vote, the 5-3 (plus Brandeis) split was apparently turned into a 5-4 split the other way, with the deciding Justice on the fence in the second case until the last minute.
So, for example, the view expressed by some scholars that the Court invalidated the minimum wage law but not the night work ban because the former allowed corporations to exploit workers through underpayment but the latter did not could only be justified if one could show that this was Justice Sutherland's rationale. But this would be a caricature of Sutherland, who believed in liberty of contract, and was a strong advocate of women's rights, but had an occasional soft spot for what he considered public-spirited regulation, as evidence by his majority opinion upholding zoning laws in Euclid v. Ambler Realty.
In short, if you want to do good constitutional history, don't extrapolate wildly from the reported votes of old Supreme Court cases.