D800 activation of VR with AF-ON: feature or bug?

With my D200 I'd gotten used to the AF-ON button not activating VR, which made a lot sense to me.  This is the behaviour described at https://nikoneurope-en.custhelp.com/app/answers/detail/a_id/25406/~/vibration-reduction-(vr)-functionality-when-using-af-on-button.

With the D800, however, VR is activated by AF-ON.  Is this intentional?  I can't see any reference to this in the manual, or any setting to change the behaviour back to what it was pre-D800.  Perhaps I'll just get used to it.  Maybe it'll make sense to me one day.  But for now, I'm just curious why this changed and whether it is documented, or whether this is just a bug.

Thanks,

Mike

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