The issue, I think (wearily), is slightly more complex than that. David is trying to give the impression that his work - as well as being self-published (as you say, a perfectly legitimate and respectable outlet) - has been published: in the sense of being accepted by someone else as a work which the someone else has then published. The act of being published by someone else is a kind of legitimisation, an acceptance of his efforts, by a third party - implying merit, credibility, etc. I quote David's words to Don Firth:

via simple links, you will find here a list of some of the places I've been published in, as well as the self-published website itself and info. on the original A4 paperback...

Actually, no, you won't find any places where David has been published in the conventional sense of the word. He has certainly self-published, but that, in itself these days, is vanity publishing and is no way any indication of merit. By implying that he has been published independently of himself, David is making a false claim to enhance what he does.

I'm sorry that this all becomes so incredibly tedious, but it's this type of obfuscation that does get up the collective nose.