Of course, this was decades ago and today would be called "artisanal" wine making.
Partly. There is some natural level of sulfites present in wines - very dependent on the terroir, and then the rest comes during the manufacturing process; some sulfites may be added directly so the wine does not spoil.
There are wines that do not contain any added sulfites and even then may cause trouble to the sensitive persons if the sulfur content of soil is naturally high. Some manufacturers therefore also add info about total measured sulfite content to the label.
And nowadays, not only demijohns or wooden barrels are used to hold wine; of course stainless steel vessels, but also concrete vessels and even things like the Georgian qvevri underground clay vessels or amphorae are having a comeback.
Sulfites and sulfates are very different, though related, and the sulfites are the things in question that have required warning labels.
I hate to be the grammar scold constantly, but swapping "i" for "a" is a weird category error and it's quite the deadly difference, like lowercasing "MegaBytes/MebiBytes" or capitalizing "kilobits per second", geez.
Chemistry has a lot of fiddly notation. My mother summed it up thus:
Johnny was a chemist.
Johnny is no more!
What Johnny thought was H2O, was H2SO4!