Giving the PA option of tilting each box (one on top of the other) to direct the sound as needed toward the front and toward the rear of the audience.

As you may be aware, usually hung with bottom directed to the front and above ones directed toward the more distant in the audience.

As you may be aware, vertical dispersion in line array is dependent on frequency.

As you may be aware. In a large home theater application with 1 box, you might need to be a fair distance away before your standing verses siting would sound similar in the higher frequency range, due to the narrowed vertical dispersion in the upper range.

As you may be aware. It is essential that there is no distance between the horns so the edges if there are any need to be cut off so that the horns will integrate together.
Even then one can expect a little comb filtering to occur.

In direct radiators like dome tweeters it is more the distance from the center to center of the drivers that determines comb filtering interference between drivers as the frequency rises. IMO horns are superior to direct radiators at reducing comb filtering.

This is the reason why side by side positioning of either drivers or speakers is to be avoided if at all possible unless the frequency is limited to bass.

[this may be info you are already familiar with, or perhaps you have some different ideas to share]
Barry