Brine strength, and why you cannot reduce the salt
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The two jobs salt does
Salt draws water and dissolved sugar out of the vegetable, which is what feeds the fermentation. At the same time its concentration in the brine suppresses most organisms while the acid-producing ones tolerate it. That second job is the safety function, and it is the one lost when the salt is cut.
This is the single most consequential difference between the two crafts on this property. A quick pickle is safe because of acid you added and can measure in the finished jar. A ferment is safe because of a condition you maintained for weeks, and salt concentration is most of that condition.
Why low-sodium versions do not exist here
The extension guidance does not offer a reduced-salt fermentation recipe, and that is not an oversight or a conservatism to work around. Reducing the salt in a fermentation brine changes which population establishes, and a ferment that goes the wrong way does not reliably announce itself by taste. Quick pickles are where the reduced-salt recipes live, because there the salt is not doing the safety work.
Someone will ask for a low-sodium fermented pickle, because it is an obvious product and a reasonable thing for a customer to want. The answer is a quick pickle with reduced salt, not a ferment with reduced salt. They are different products and only one of them has published guidance behind it.
Getting the concentration you think you have
Weigh the salt and weigh the water. A brine measured in cups is a brine whose concentration depends on which salt you scooped, because flake, kosher and pickling salts do not have the same bulk density, and that is the mechanism behind the salt page. Then dissolve it fully before the vegetables go in: undissolved salt sitting at the bottom is salt that is not in the brine, so the top of the vessel is weaker than your recipe says and the top of the vessel is also where air is.
Record the weights per batch. A ferment that fails is diagnosed from the log, and brine strength is the first thing you will want to rule out.