I use LifeMiles to check availability; not much seems to have changed except there is zero availability out of Auckland on any date. For the last week in March 2019 ex-Bangkok LifeMiles is showing 2 in J to FRA & CDG on 26/3 and FRA on 1/4. MUC nothing (always a brave choice of destination with TG) and same for ZRH. Limited Y availability most days, most destinations. No F. In contrast there are 2 seats available on every flight to SYD in J but none for F in that week. I suspect it's simply a matter of demand management. BTW (your favourite hobbyhorse I know) there are no F for Bangkok-SYD that week which may mean none may be available because the 747 may not be flying by then? Just saying