phiggs fair point, I would have been more accurate to say brakes off to brakes on. Talk of brakes, chocks and 'aircraft moving under its own power' are nearly but not exactly synonymous.
A few things that are certainly red herrings interms of logging time as a pilot of civil aeroplanes are: startup to shutdown, Hobbs, flight time for engineering purposes, any clubs method for charging for rental, how things are done in the military, on helicopters or under other jurisdictions.
The new FCL wording is clearly an attempt to clarify this issue but, like the rest of the new legislation, is poorly worded with many unforeseen (but entirely foreseeable) consequences. To steal the above example of taxying out, but having to carry out a rejected takeoff and FCL suggesting that the time is not loggable is very odd.
if you are carrying out the duties of a licenced pilot and are also carrying the legal responsibilities that go with it, it is appropriate that the time should be logged. If the authorities would not tolerate an unqualified member of the public carrying out certain actions, but instead demand an appropriately qualified pilot, then thatntime should be recorded accordingly. You can guarantee that in the event of the rejected takeoff you would be recorded on the incident paperwork as part of the operating crew.
As others have rightly said, if you question the legitimacy of recording taxy time associated with a flight, have a think about arguing your point of view in court after busting crew duty limits, flight time limitations or having had an accident.