While I am not privy to the signal path layout of your receiver, if I were designing a unit where the delay of individual channels or groups of channels was possible, and the bass management portion of my unit mixed the lowest frequencies of several channels together in its bass management section, I would put the delays into effect after the lowest frequencies were summed, not before.

Because the ICBM is not designed to provide delays, it relies on the incoming signals to arrive at the ICBM inputs with the same timing as the original source outputs. Delaying one or more channels before the ICBM will mean that the frequencies below the selected crossover point will be mixed with those lowest frequencies slightly out of time with each other. Depending on the amount of any delay(s) and the frequencies being mixed, this will have anywhere from a negligible effect to an easily noticeable effect. This is why it is easiest to leave all the delays at zero or set identically and not be concerned about the mixing of sub-bass frequencies with a time shift in place.

I only suggested trying your system both with and without differentiating delay settings for you to hear the results. Without differentiating delays, the sub-bass mixing will be unaffected. With differentiated delays, the arrival of sound from each speaker is timed such that the listener in the ideal location hears each speaker as if it were equidistant from the listener. Which is more important to you?