I got the impression that he was talking about inexpressible rather than inexpressed? There's a huge amount of tacit, implicit, craft knowledge that isn't or is only poorly captured in text, not just from evolution.
I mean, there could well be a text about the exact experience of hammering in a nail, or the precise amount of time and intensity to make eye contact when crossing someone in a given city, as modulated by perception of social status, etc. but there probably isn't.