This whole issue is a distortion of what citations should really be for.
When I write a document, I’ll cite relevant documents. If I’ve written on a similar topic before, it may well make sense to cite myself — rather than copying it all out again.
Yet in this silly world, citations become currency, which benefit the authors of the cited document; so if I cite myself, however sensible, some will claim it’s bad form, a way of blowing my own trumpet and somehow nearly fraudulent.
As I’m not an academic, and won’t perish if I don’t publish I can ignore this; but from my position it does seem ever so silly.