There is no reason an ACH should ever take 7 or 10 business days.
Given the quick speed of an ACH "in the real world" it can be assumed with a fair bit of confidence that Intuit, Stripe, or some combination of the two, is investing the cash for "overnight rates" as another poster has stated.
They'd rather collect the 3% on CC payments so there is little incentive to move the ACH money with speed (other than just being a good, ethical business that treats customers fairly).
Just one more way that Intuit wears their disdain for their customers on their sleeve, so to speak.
