I was sort of wondering the same thing.
My horse doesn't get too much, when it's soaked it fluffs up to about half of a small feeding bucket (like 5qts?) But I have given him 2x that much at once and he just gobbles it right down.
I think it digests quickly because it's grass and very natural for the horse. Much like grazing on good grass.
I think you're ok. And I'm glad you feed them soaked, I am so worried about feeding dry, they are like rocks!!