I don’t have any technical insight to offer here, but I can tell you that there are some known issues with the current boolean modifier. They used to use another third party library called carve for the boolean modifier, but that supposedly caused booleans to fail in other situations and is no longer maintained, so they removed it in favor of using their own code.
A developer named @howardt plans to improve the current boolean modifier:
Maybe he can shed some light on why the current one fails in this situation.