I'm with Adam on this one.
I/c time of the beast commences once the fan is running when it can kill folk or bend the 'plane. Control of the vehicle on the ground requires certain different but necessary skills too.
Perhaps one should log ground time as "pax" time though who is i/c at that phase when 'solo', I couln't possibly say !
To meet all folks' needs log books could/should possibly have four columns I/c on/off plus flying time t/o to t/d !
However after 40+ years of logging times I am unlikely to change now - it is a pretty personal thing after all.
mike hallam.