The recommendation in the Fowlers Preserving book is to open the jars, pour into a saucepan and boil foods like curries, bolognaise, soup etc for 10 mins before serving. Which is no real issue. This was added in the later versions of the book after advice from the Department of Health (Victoria I think?) to deal with potential issues of Botulism in foods that had a pH higher than 4 (and that you didn't add acid to, usually in the form of lemon juice and/or citric acid).
I've only been preserving for 5 years or so but I grew up with a pantry full of preserves. My olds were over on the weekend and Mum saw the cupboards full of preserves and it got her talking about how she used to do 400+ jars of fruit, veg and pickles every year when I was a kid. She is very happy to see me continuing the tradition using her preserving kit.
And yes, the preserving kit I have is older than me, the thermostat is in Fahrenheit. Unit converter app FTW.
Cupboard needed reinforcing with bricks to deal with the weight of the preserves. Tomato sauce, plum sauce, passata, fig paste, jams (fig, apricot, strawberry, plum), zucchini sweet mustard pickles, zucchini salad, pickled jalapenos. Once the bug bites..... it's a bit like buying your first kit beer.
Nectarines and peaches