There are likely other metadata he may be missing here: - in particular dates/times/time periods which may be useful for the historians. - others? - general forms of useful metadata from a database perspective?

This seems antithetical to the broader idea of concrete! His definition of concrete isn't very concrete is it?

Is he calling to mind Webster's (1913) definition:

To form into a mass, as by the cohesion or coalescence of separate particles.

If this is the case, then having small notes or excerpts with short indices is clearer for small particles which could then be glued together for summarization.

Taking note of any serious ideas which are contrary to our own conceptions is important because this may lead us to new realizations about concretes which in turn leads to new frontiers of knowledge.

One must find a way to push through potential cognitive dissonance to compare ideas and sharpen them over time.

His definition of these could stand to be more concrete.