Two claims, in one paragraph, are inconsistent:

Justice Alito was never seriously believed to be more conservative or even more overtly conservative than John Roberts

and

John Roberts [was] still widely, if wrongly, billed at that time as a temperate bridge-builder

I don't see any necessary inconsistency. Roberts was seen as a moderate conservative at the time of his nomination. Most observers think that Roberts has turned out to be substantially more conservative than he appeared at the time of his appointment, but that realization has set on only many months after he, and Alito, were confirmed.

So there's no contradiction in saying that Alito wasn't considered to be more conservative than Roberts at the time of their nominations, and that expectations of Roberts as a temperate bridge-builder have been pretty much dashed.

But I do think that Alito was considered by many to be more conservative than Roberts, both at the time of their nominations and today. Still, that's not an inconsistency in the article; that's just an incorrect statement.