Has anybody asked the CAA whether Ghengis's, or Beagle/Bose's, interpretation is correct?
As a matter of fact, they have. According to the 'Policy Section' of the Licensing and Training Standards Department (what used to be PLD), the CAA will not accept as valid towards the issue or revalidation/renewal of any licence or rating any 'flight time' when the aircraft has not left the ground.
You are, of course, entitled to record anything you wish in your personal logbook, provided that you at least record the minimum required by Article 79 of the ANO. However, any time recorded when the aircraft did not leave the ground is as worthless as time spent sipping G&T in the comfy seats down the back.