That's an interesting bit about children taking their mother's name. I know that often to distinguish between cousins of the same name, probably named after the same recently deceased ancestor, they'd be identified by their mother's given name. Thus giving rise to Jewish surnames like Dvorkin, Chaikin, Sorkin, Rivkin, Rachlin, Estrin, etc., that are all women's names in a genitive case.
But is there something else going on here? I have relatives who also came from Soloveitchiks on their great grandmother's side, whose great grandfather took his wife's name when they reached Chicago. (There they made it Solovy.) I always presumed that her name had more prestige, or was easier for Americans than his difficult name (Knishevitsky). But your "Shorris" story makes me wonder if there was some naming custom alive in the Soloveitchik clan that made taking a mother's surname more common somehow...
I get that there's a difference between being referred to as your mother's before the era of surnames, and consciously choosing your mother's (or wife's) surname after the era of surnames.
Still, your story, specifically as a Soloveitchik whose family chose Shorris, made my mind start to wonder...