That fitting is a fridge manufacturer issue. The assumption during install is that the connections inside the unit by the manufacturer are "good" and the only ones that need checking are the ones made during the install.
Maybe those assumptions need to be "re-thought."
When I buy a house appliance, I assume the wiring and plumbing connections inside are OK and I only need to worry about plugging it in or hooking it up. Taking it apart to meter the connections and leak check the fittings internal to the unit has never come up at my house.
Sounds like this one was a "Friday Unit" and QA missed the loose B nut.
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