Where does the final approach segment begin on an ILS approach?
No arguments needed, it's very specifically defined. According to the FAA's Pilot/Controller Glossary under SEGMENTS OF AN INSTRUMENT APPROACH PROCEDURE:


  c. Final Approach− The segment between the final approach fix or point
  and the runway, airport, or missed approach point. (See ICAO term
  FINAL APPROACH SEGMENT.)


So it starts at the FAF, which is defined in the same document as:


  FINAL APPROACH FIX− The fix from which the final approach (IFR) to an
  airport is executed and which identifies the beginning of the final
  approach segment. It is designated on Government charts by the Maltese
  Cross symbol for nonprecision approaches and the lightning bolt
  symbol, designating the PFAF, for precision approaches; or when ATC directs a
  lower-than-published glideslope/path or vertical path intercept
  altitude, it is the resultant actual point of the glideslope/path or
  vertical path intercept.


In your example, that means the final approach segment starts at JAKOR. I may be wrong here, but your original thought might have been that the final approach starts when you're established on the glideslope, which could be outside JAKOR. That makes sense in a general way, but it isn't how the term is defined.