FWIW, if you'll measure the distance from the center of the aperture of your "carry-handle detachable A2 sight" to the top of your flat-top receiver, then remove the "detachable" and install the ARMS #40 A2 BUIS, (making sure to flip the sight "up") and measure the distance from the center if it's aperture to the top of your flat-top receiver, you'll find their identical.
Seems, is what happens when you don't use your ruler or your noggin.
Mike
ps - the BUIS (back up iron sight) is just that and as such is "lower" only when in it's resting position, when flipped "up" (provide your EOTech is mounted directly to your flat-top) it will be at "co-witness" height, and your red-dot should be setting directly atop your front sight post. (provided your using the IBZ 50 yard zero method for both your EO and BUIS)