I can see why people would say this about "Muslim" girls; in quotes because many of the ones you meet clearly give about as much importance to religion as your average Colombian.
The problem is, particularly with the educated ones you're likely to meet is they have no real convictions. Their life may be a facade of religious directions that don't mean anything. In itself "because Mohammed" is not really a good reason to spur someon's behaviour and many of the genuinely modern Muslims are virtually agnostic. In particular I've spoken a lot with North Africans. Religion is virtually no part of their lives. Some say they are basically agnostic, others are apostates. The reality is with a lot of those countries is that a considerable portion of the educated class play the same game as Democrats pretending to be Christians.
For wife material the best thing you want to look for is someone who has deep personal meaning behind the convictions you find attractive. As an example I never smoked as I grew up worrying that my father might drop dead at any moment from smoking. That's a lot more conviction that PC Plod coming in and telling you to keep away from drugs, fags and booze. For a woman does she want to have a child because she can't wait to parade her child, Beyonce Knowles Smith or does she have a desire to do a better job than her parents.
Muslims societies expect a lot, but in private and over time there's no reason for those things to actually exist.
On a thread something about red flags someone got a lot of up votes for saying something like, "be careful of women who talk to waiters and other service people like garbage."
That's one of the thing that has stuck in my mind most from this forum. It's in the same vein as Kanye West's, "judge a person on how they treat someone who can do nothing for them".
Last year I was in Bangladesh and met a girl, a Muslim, but like most of the upper-middle class+ there she was far more interested in Game of Thrones, Ed Sheehan and having a baby with blue eyes than Allah Akhbar. They just want to have money, 1 child and go on holiday. Religion is just a few festival and words.
Some guy made an advance at her and she went a off the wall at him. Completely humiliating him in public. I'd never seen anything like it. But to me from the off, she was the sweetest and most feminine, giggling, playful girl I'd come across. For the first week my balls were aching badly because of the copious amounts of T her calling me her king etc. was making me produce.
One day she was being very sweet and playful, telling me how much she loved me and how her children would have, "lii
ggghttt s
kiinnn, b
lueee ey
yyes, tee-hee-hee." and pretending to drink my blood because I turned her into a monster. I never saw her again after that and virtually never spoke to her again.
She had no real drive beyond superficial things and feeding emotional states she liked. I'm sure her eventual husband will also think she is the sweetest little thing and believe her when she tells him she's a virgin. She'll always think she's a good person and refuse to engage with whatever she don't like she can get away with. She wanted to know what I thought of Islam. I told her I had a negative opinion. When I started digging out the Pew data etc. she said it was "fake news". As long as I didn't rock the boat she's be fine.
In short there is no real meaning to girls who are propelled by cultural-religious indoctrination and biology. If they don't have a personal meaning, it's bullshit. They're like water being channeled into whatever the best options they get presented with.
While I was there her 3 year old niece was sexually assaulted by a 10 year old boy, one of her friends had an illegal abortion willingly provided by a hospital and she sent me photos of her sister balling her eyes out after the sister's husband beat her. Never heard of any of those things happening anywhere until I spent 1 month in a Muslim country where on the surface the middle-class people seem very nice and friendly.