Could it be that the re-musters mentioned were never in the R.A.F. and as members of R.A.A.F. and R.C.A.F. could not be transferred?
Probably destroyed my own argument as a quick google shows
Roy Max as short service commission R.A.F. Aug '38 - July '43
R.N.Z.A.F. as squadron leader
1947 permanent commission in the RAF as flight lieutenant
Jan '60 promoted to Group Captain. A rank he had had as co of 75(NZ) in '44.
n.b. As 5 year old in '43 "Maxie" was my hero airman.