I have had a further thought or two about the word Command.
In General
It is possible to be In Command of a vessel/aircraft/ machine however you can not Command (verb) a non sentient object ie you can not Command a machine, your utterances will have no disenable effect.
Command infers authority to control humans or other beings eg a working dog, by the use of words (verbal or writen).
In Aviation
A Pilot In Command (PIC) implies a great deal more than mechanical control (as in manipulate the machine so as to achieve flight). The PIC has legal standing & responsibility, must by convention & I suggest, law, be licenced ie not a student .
It is tempting to think of a solo (unlicensed/student) pilot as PIC, as they are the only person on board, so must if circumstances (safety of aircraft) dictate, make authoritative decisions. However this is to ignore the role of the students Instructor, who is in fact the only Commander (PIC) in this relationship/situation. Note; The Instructor need not be in the aircraft to maintain this relationship. By law & convention, there can not be two PICs for the same aircraft/time, ergo the student can never be PIC.
CASA/RAA/FAAA and any other authority that uses the words Pilot In Command for an unlicensed pilot, are simple incorrect, inconsistent with other aviation rules, regulations & custom. Their intentions may be known/understood, even supported however the terminology does not accurately reflect the situation, that the student is under the Command of the Instructor.
Just because a bureaucracy (staffed by fallible humans) draws up a regulation, this does not mean it is necessarily worded well (grey areas), correct (wrong) or consistent with (supports/contradicts) other regulations.
Those who blindly refer to/quote the regulations, without critical thought, undermine democracy and ultimately the rule of law.π