That's why it IS legal to log...because the FA does not define that bucket. There is also no FAR that says you can only log time as defined by the FAA...you can log whatever and however you want. You can even falsify your logbook all day long as long as you never attempt to use any of the false time for FA currency/aeronautical experience, or use those false totals on any federal paperwork (ie medical).

You are only required to accurately log the minimum time required for needed currency & aeronautical experience for certs/ratings you apply for. Other than that you can log nothing, or anything at all.

Your logbook is not really an official document...certain entries for required endorsements, sign-offs, and aeronautical experience are official and need to be correct.

As an example there are highly-experienced folks who log only time/LDGs/IAPs needed for currency even though they fly much more.

Another example...I knew a guy (all around idiot) who padded his logbook to build time. He got hired by a regional but for his checkride he had to fill out an 8710...at that moment he realized that while lying to a bottom-feeder regional is not a federal crime, lying on an 8710 is. He put his correct time on the 8710 (still enough for the checkride), but somebody noticed the delta and he got fired. At least he didn't go to jail.

Correct. The student does not need a ME rating (how would he get one?), but the instructor must have a CFI-ME rating to give dual to any student in a twin.

That's exactly what it would be if logged as total time, but see my comment about future employers above.