FCS Explorer is not expressing a pet theory - he is quoting verbatim the Boeing 737 Flight Crew Training Manual. Vref + 5 is the number for that type - applicable to all series fitted with autothrottle from the -200 ADV to the latest.
Note the use of the word 'recommended'.
Only once have I seen a statement in a company operating manual that quite clearly said that they had developed some differing procedures as a result of extensive operational experience, that their procedures were FAA approved, and that they accepted responsibility for the consequences of having changed the procedures. In the absence of that statement, I have always assumed that if a company issues crews with the Boeing FCTM, the intent is for it to over ride the SOP in much the same way as the AFM does.