I htink it is fair enough, tbh.
If a person is needed abroad, to serve their country, and they need/want stability of education for their children (due to moving around a lot - I was a forces child, i know what it is like. I never lived in a house fo rlonger than 2 years when I was growing up - moving around country to country).
It makes no difference whehter the spouse is working or not, or "available ot look after children" - the issue is that the children would not be getting a decent grounding - no long term friendships, no continuity of education - and this would be true whether the spouse was working full time or a sahm.
wrt to SN residential school being so very different - i am no longer sure that it is. I obviousl yhad ot look at it for very different reasons, but if we had been living in an insecure place when the children were school age, I might well have considered it in their best interests.
I owuld also have looked at all the other options, but again, life is not always as simple as "well, change your job then".
we have lived in soe places where I woudl not want to have my children educated/running around freely. should I (theoretically) have therefore home edded them, and restricted them in that way, or send them to boarding school where they get more freedom, more continuity etc?
as it happens, dh did just change jobs (well, moved sideways, in linked positions) so it no longer applies. but he may well be sent abroad again - and so it would become a consideration again (of course life is extra complicated as we now need to consider SN education too).