Here is a source that establishes the use of the specific phrase you mention coincident with the 'airspace redesign'. It seems to clarify the timeframe you seek but is not in the publications you specify, so I put it here separately. The document deals with charting implications of the ambiguity you describe.
The front page of the document for reference.
A visit to an air museum with an archives library turned up several old copies of Airport/Facility Directories, one of which helped to narrow down the time window for this question.
In the A/FD edition current August 18 1994 to October 13 1994, the "Airspace" item in the "Legend" section did not contain language explaining that extensions ...
This is a dismal answer, but:
Instrument Rating Test Prep 2004, published 2003, contains a paragraph closely matching the one mentioned in the question: "NOTE: AIRPSACE SVC "TIMES" INCLUDE ALL ASSOCIATED EXTENSIONS..."
The partial scan found on the page I linked above matches the formatting of official Airport/Facility Directory Legend -...