@Joseph, when you do a shidduch call and like you said, ‘brainwash folks about your kids’, people still have access to more material. Someone interested in the girl/guy has different ways to receive more accurate information, even if you only speak about the positive aspects of your kid. A girl in seminary, on the other hand, has none of that.
She’s surrounded by only what the sem wants her to hear. That kid is isolated from reality. She has no other ways to learn what it’s really like. They don’t tell your daughter what it’s like having 4 kids and morning sickness and still have the entire burden of bringing home enough money for her entire family, they only tell her she has the most wonderful zechus of having her husband learn without having to worry about supporting his family.
So yes, that’s brainwashing.