I think we'd have to agree that sometimes the "experts" ignore reality. The later advice about the picnic lunch seemed to me to be a bit of a look back at the fact that lots of people have lived through horrible things "they say" you shouldn't do.

The end-point acidity of a homemade vinegar will depend on what yeast varieties get into the mix. If it's a concern, there probably are some pretty good tests described in some of the old cooking/canning books, but I don't have granny's library at hand to check it out.

John