That very strongly suggests to me that the updates in question cannot be "turned off"...that they're considered so necessary that Apple has built a backdoor into OS X/macOS to ensure that they can't be ignored.
Any additional info and/or insights will be appreciated.
No particular insight, but given Apple's extreme aversion to backdoors as security risks, even acknowledging its existence is surprising. However, given recent security issues apparently exacerbated by institutional Windows system managers failing to apply security patches, I can understand why Apple would want to have that ace up their sleeve.
