These stories all hail back to around the time of the Second World War, a time when women, even into their twenties and older, were quite often subjected to spankings from husbands and boyfriends, as well as fathers and uncles.
There seems to be no suggestion these military canings were anything other than semi-official at best, and often totally unofficial.
As a child of the 1950s and 1960s, I remember well the cadet forces attached to many schools and also as separate institutions in their own right and corporal punishment would often be used for misdemeanours in exactly the same way as it was used in schools.
My best guess, rightly or wrongly, is that probably a small number of younger females in the armed services were subjected to spankings and perhaps the odd caning but that officialdom, if it ever knew the truth, simply turned a blind eye.