Yeah that's the narrative from Cerulli but I think he's got the chronology wrong, the death of the Imam at Ceel Cawl seems to have taken place much earlier than the invasion of Mogadishu, a century or more.
There are two oral histories from the Hiraab oral tradition, the story of the death of the Imam of Ajuuraan at Ceel Cawl, and the story of the takeover of Mogadishu. Cerulli puts the Imam's death later in his chronology and the Mogadishu takeover earlier, but abtirsi tells a different story.
The story of killing the Imam of Ajuuraan at Ceel Cawl is the origin story of the Hiraab Imamate under the Yacquub dynasty, where the Darandoole (the predecessor of the Hiraab) gather together and make war on the Ajuuraan. In this story they are a subject people of the Ajuuraan who are persecuted by the Ajuuuraan leadership.
The story of the takeover of Mogadishu takes place much later on, a hundred years later, as the Hiraab take Mogadishu the great prize of Banaadir. This story does not mention Ajuuraan and the Hiraab are no longer a subject people but under their own leadership.
Clearly the two stories the Mogadishu story is of an ascendant, later kingdom and the Ceel Cawl story is of an earlier, subjugated people. The chronological order should be clear.