This is OS functionality, so it would be akin to iCloud helpfully synchronizing your vim recovery files across your Macs (via a roundtrip to iCloud) without you ever asking it to - not a change in vim.
This is why this is worth sounding the alarm over - it's an OS-level change that affects all apps, not just Apple's.
That's a good point, and is part of the reason I have iCloud turned off completely -- so I don't have to think about individual cases.
Obviously, it's completely possible that mdsworker or any of the other dozens of Apple daemons is slowly leaking my unencrypted RAM or swap files out to 17.x.x.x or somewhere else I've allowed in my packet filter configuration.
But that is the line between enhancement for the majority and malice for the targeted. As long as I force Apple to cross that line before causing me any damage, I feel comfortable trusting them (their corporate policy, their auditing, their hiring, their systems administration, etc).
This is why this is worth sounding the alarm over - it's an OS-level change that affects all apps, not just Apple's.