One thing to consider is that by adding a reference frequency input via the coax, we make the voltage of the coax available via a series resonant circuit. So, any alien voltage (think ESD voltage) now finds it's way to the sensitive ports of the oscillator of the LNB chip.
The standard F connector connects inner pin first before ground connection is made. This is like the audio tulip plug; the hum of connecting an audio source to an amplifier via tulip has blown many speakers.
With the F connector, the inner pin can launch ESD voltage to the inner oscillator before ground is made.
In my LNB's, I have modifications to make them run on low-noise 5V (for the PE1CMO kit) and to avoid connecting 13/18V to the 5V input I permanently added an F->BNC converter, tied ans secured through heat schrink tube. This has the advantage that on connect, the connection is made to ground first, so I don't have the ESD issue.
Perhaps something to ponder,