With Lt. Vos (Royal Navy liaison officer) it was really just a shot in the dark. I have not been able to find out more about this man and it could well be that he was not SANF at all. An anglicised Hollander in the RN perhaps?
As for the rest of your comments, well...I'll accept a small element of truth in what you've posted but I cannot agree wholesale with your assumptions about South Africans, of their bilingualism or their willingness to serve in the Royal Navy, whether of British or Dutch/Afrikaner descent. The situation in SA at the time was a heck of a lot more complicated than most people understand but within the armed forces there existed a strong sense of unity with mutual respect and admiration between the two population groups. Wherever these men served they always very proudly presented themselves as South African and whenever the opportunity arose they did silly stuff together like playing rugby, Zulu dancing and singing "Sarie Marais". I'm not sure if the RN condoned or encouraged it but the number of group photos of South Africans taken aboard RN ships gives one the impression that they very much stuck together.
To relate this seemingly irrelevant topic to the war in the NEI, I'll quote from the memoirs of stoker Norman Macdonald (later Lt, SANF) aboard HMS DRAGON:
"When the invasion of Java became imminent the Dutch women were offered passage to safety in our ship. They refused, much to our regret. The South African sailors in our ship became the envy of the British seamen when they heard us speaking to the girls in Afrikaans!"
Bilingualism had been official SA government policy since 1925 and for high school students both English and Afrikaans were compulsory subjects. I will agree that Afrikaners were (and still are) people of the land and more likely to enlist in the army than any navy but quite a number chose to go to sea, received naval training aboard the SA Training Ship GENERAL BOTHA (named after the Boer hero) and ended up in British service (mostly in the merchant marine). Here I'm reminded of two outstanding individuals namely, Adolph Gysbert Malan (better known as Group Captain "Sailor" Malan - the famous RAF fighter ace) and Lt.Cdr. Hendrik Hugo Bierman (later Admiral and Chief of the SA Defence Force). Rather than not wanting to serve in the RN, it was more a case of the Royal Navy not wanting colonials, let alone non-British South Africans. The RAF by comparison was far more receptive and I have quite a list of GENERAL BOTHA-trained men that ended up in that service. Here are a few Afrikaners that I know of, that were accepted into the Royal Navy during WW2: Lt. Pieter de Kock (HMS GLENEARN), S-Lt. Ferdinand van Eysen MBE (HMS ARUM), Lt. H. De la B. van Alphen (HMS KEMPENFELT) whose grandfather was apparently a Dutch admiral and S-Lt. R. Franck who was offered a commission in the RAN after the war.
You stated: "Afrikaners would be more likely to (be) bilingual but the English group not so much so."
Again, not entirely so. It really depended on which region one was from or which profession one was in. For instance the commanding officer of HMSAS NATAL, Lt.Cdr. Hall was a mining official from Krugersdorp in civilian life, his First Lieutenant L. Alexander from Knysna, his Surgeon-Lieutenant R. Skea from Bloemfontein and his ASDIC officer Lt. Richards, a veterinary researcher from Deelfontein in the Orange Free State. If you know any of these places, you'd know that these men would have been rather fluent in both languages.
And while on the subject of the frigate HMSAS NATAL, I must mention her amazing feat when she sank U-714 on March 14, 1945. She accomplished this on her very first outing with her crew still in training, scarcely 3 hours after leaving the builders yard at Newcastle-on-Tyne!
Of course the Brits, to this day, still have a thing or two to say about it (like they always do!), claiming that their destroyer HMS WYVERN (sometimes spelt WIVERN) had done the deed and deserves the credit.