Actually what's quite interesting is that people have the view that British or American women are seen as very independent and women from other countries as 'submissive'.
The longer I am in the UK, the more I am of the view that many women in the UK hold very traditional, 'family values'. E.g. a lot of focus on what the job of a boyfriend or partner is, whether they have a decent income, family background, whether they want to settle down. Almost all women I work with plan to get married and have a wedding, or had one. Lots of women want to work part-time or not work at all, lots of interest in home-related hobbies like interior design, baking etc. Women talk about home and family life so much of the time, which implies it's of high importance to most women. Went to work Christmas drinks today and that was the entire evening's conversation - home and family life, houses, children, family social events.
Growing up in Scandinavia I never really knew anyone or anyone's parents with these kinds of priorities, e.g. marriage/ weddings or being a SAHM was pretty unusual, women would often earn the lion's share of household income etc. Conversation would be about politics, economics, news, travel, hardly ever would you socially discuss your housing or family matters.
I really don't think the OP's brother is that interested in traditional/ submissive. I mean, a girl who's left Armenia or Argentina all by herself to live in the UK is hardly going to be submissive or poor, is she? She'll likely be well-educated from a wealthy family, coming to the UK to grow professionally and personally. Maybe he's just into that.