Funny how perception works. You call him moderately liberal. I'm not sure under what context your using that label. I would call him conservative since he asks us to apply interpretation, at least to begin with, strictly based on context,culture,time, and pattern. His approach seems scientific and thorough.
You're looking at his methodology which appears to be a basic inductive technique....nothing wrong there. I'm looking at his presuppositions about prophecy, parables, and revelation (apocalyptic). They are moderate to liberal.
1. Prophecy - he restricts the vast majority to the "sitz im leben" of the author.
2. Parables - he allows only one meaning be derived.
3. Apocalypse - Again, restricted to the early church "sitz im leben."
Those are not conservative assumptions about scripture.