Yes - he did say

the best social singing is, in my experience, unaccompanied and because of that the bulk of the songs on this site are songs that I sing unaccompanied.

In the 60's and 70's the status of unaccompanied singing was much higher within the folk scene, and most of my favourite albums from the revival are albums where the majority of the material is unaccompanied. This approach has fallen out of fashion and the commercial pressure is for modern day 'folk artists' to have, at most, one or two unaccompanied tracks on their albums, if at all. I have always thought of myself as first and foremost an unaccompanied singer so it was quite a shock to me to realise that, although I have now made 10 albums, I have never included a solo unaccompanied track on any of them.

To be fair, the first seven (of ten) were all unaccompanied - maybe the current run of three will be a blip.