I would be surprised if CASA went along with the use of 77kg these days unless an operator could put up a very strong argument to undervalue the CAAP ?
77kg is the standard figure still used in the PPL and CPL exams, esp for loading chart echo.
Can't comment on those for ATPL.
By using them in the exams, i think CASA are doing exactly what you mention in the second part of your paragraph.
Cheers
Jas