Thunderhead Peaks Fortress Design Question

What was the motivation for the dwarves to have added the large holes in some of the smaller hallways of the Thunderhead Peaks fortress? From a game-mechanic perspective, these were obviously included to provide a use for the Bond of Faith mount mastery. However, unless the dwarves were amazing acrobats I don't suspect that they would be able to reach the areas that are accessible with Bond of Faith as they are currently implemented.

In-universe, the best use-case I can infer is that they were meant as false-floors to capture/injure looters and invaders. This rationalizes the hallways that dead-end by putting something shiny and valuable at the other end of the pit (like where some of the dwarven chests are at).

Alternatively, the gaps could have been used as a defensive measure to control the number of simultaneous attackers the dwarves would have had to defend against. The gaps could have been spanned with a bridge (likely made of rope and/or wood) that would have rotted away over the past several decades. Given the height of the hallways, this would have allowed arrows to arc into the narrow passageway at the other end of the gap. However, the lack of other defensive measures like murder holes or spikes suggest this may not have been the case.