The issue that Rated D mentions is that there is NO study of SYD/MEL flights leaving at night flying for 23 hour plus Tours of Duty to London.
A lot of the Monash study was on MEL-LAX a much shorter tour of duty, only 5 hours time zone change and both sectors left day time body clock.
Scientifically it’s not valid or of very poor validity.
No study has been done as it’s been considered to be unsafe, unwise and hence illegal.
Any study has to be of an equivalent tour of duty AND be long lasting. You may have to do it for many years.
Joyce shouldn’t be able to do it period. Let alone do it with worse protections for crews health.