such as iodine or anti-caking ingredients and such.
All ferments are probiotic with various strains of lactobacillus in them. Canning and pickling with heat and vinegar are not probiotic, and the only benefit from them is shelf life. I'm not really sure if vinegar kills the good microbes, but heat most certainly does. Ferments need to be stored in the fridge when they are done fermenting. The fridge doesn't stop the ferment entirely, but it slows it down to a crawl, and the flavors continue to develop over time.
And yes, the cabbage should be massaged/squeezed/pounded to break down the cells walls of the cabbage and release the juices and sugars in the cabbage. At least, that's the age-old concept...not really sure why, as other fermented vegetables don't say to do that. Maybe it just makes the process go faster...I don't know.
All I do know is the flavor and health benefits in unpasteurized/unprocessed sauerkraut is definitely superior to what you might find in a grocery store (unless you buy Wildbrine).