As has been said, it's most likely that mom knows full well their "hidden" motivations. It's cliche, but honestly, fits the theme and tone far better than her turning into Mari Nagare. Comedy and perhaps light chastising would flow easily, whereas heavy accusations and drama would be out of place and create obstacles that over complicate the story progression. That being said... It IS a product (art, but still), so that sort of decision would add chapters. I don't find it likely, but I always have the Kanokari reminder in my head.
As ever, thank you for scanlating.