Not sure how relevant the fact that BA/ Air NZ or QF do 3 or 4 man (or person in the gender awareness age). Further, not sure if anyone is advocating it's a good idea...
However, if anyone is saying it seems to work fine for "X" airline and hence must be an OK idea.... then please state which of those airlines will roster 3man ULH with one person based in London, one person based in SYD (but on a 9 day pattern) and another based in HK, being a "low-time" pilot....