I finally found a logical explanation for what could have happened to the liquid in the jars! This was not in their FAQ answer.
From the Kerr Kitchen Handbook (1990) ... the canning book that preceeded the Ball Blue Book ... after processing for the necessary time:
"Turn off flame (gas). If possible, move canner carefully off burner (electric). Let pressure dop to 0 of its own accord (this will take 30 minutes to 1 hour). Do not force-cool the canner by running it under cold water or opening the vent port. Force-cooling can cause loss of liquid from jars, seal failures and warp the canner lid. When the guage on the dial registers 0, or when a gentle nudge on the weight on a weighted guage does not produce steam, open the petcock or remove the weight. Wait 2 minutes before unfastening lid."
"It ain't what you don't know that gets you in trouble. It's what you know for sure that just ain't so." - Mark Twain