Some mistakes in the eBook were corrected in a later revision which any buyers were sent a link to. It still has the odd mistake in it, though (like not mentioning when some ingredients are to be added) but all in all I consider Julian's ebook to be one of the best so far along with Mick's/CBM's.
I never did get that vinegary smell either, though. I've come to the conclusion just not to worry about it. I even think that you can cut down on the cooking time a lot without sacrificing any flavour at all.
One thing to note: The only time I got a smell from onions that *could* be described as "vinegary" was when I made caramelized onions really slowly and slow-fried them for a very long time to make them really dark. However, for that to work you need to slow-fry the onions, and not cook them in water. Maybe all the water had already evaporated in Julian's pressure cooker when he smelled it and the onions were on the brink of burning but not quite yet?!