My last record of the tolerances is in my old AIP, ENR 1.1 19.11 Avoiding Controlled Airspace - page dated 25 NOV 04 and in the index last updated 23 NOV 2006. It is in my VFR Guide of 2001, but there is no mention in the VFR Guide from 2007 on.
So I would say this happened about 10 years ago for some unknown reason. You are correct though - the tolerance for the NDB was +/-6.9 degrees.
I still use the Visual tolerance of +/- 1NM buffer when navigating around a CTA boundary.