You’re not wrong, there’s certainly some bias here, but not sure what the intent was, if there was any or if it was just not thinking it through all the way. I know I’ve certainly forgotten components in projects that after review I didn’t know how I’d missed or that in hindsight were crucial.
I feel like using quartz as a gastrolith would be pretty basic, like you might as well eat those silica packets or chew on some glass if you’re going that direction. Some nice gneiss would likely be preferable, much more cultured at least.