Yep, that's not a change actually. I'm still using the 1976 edition of Putting Food By, and although I believe processing times have gone up since then, she recommended citric acid even way back then. (It's great to have around the house as a cleaning solution too so I buy it in bulk!)

IMO the key is to be religious about using PERFECT fruit. Touch wood, I've never even had a case of flat sour spoilage. Any tomatoes that aren't perfect get sauced and frozen. (1 pint of sauce in a 1 qt ziploc, they lie flat and stack once frozen, saves a ton of space in the freezer!)