How reliable are the bendairi texts. It seems like these guys are trying to project their lineage back to the founding of mogadishu to claim ownership and justify it.Yes this is very true and this is discussed by the the Tradition text piece by Cassaneli i linked above.
You see this also on the Northern-Eastern coast, visitors directly mention receiving genealogical lists and pieces of local history from record keeping Qadis on the coastal towns like Hafun.
About Southern Somalia and Mogadishu. Lee Cassaneli mentions few examples of these documents recording local histories on Southern/Benadiri area or about Ajuran(The Taxers) from families/individuals in the interior and on the coast
The Benaadir Past: Essays in Southern Somali History
Can't find the full text unfortunately but i have seen elsewhere that he makes references to them in this. But one of the documents he talks about is a chronicle set in the 17th century about Sheikh Hassan Buraale , who lived some thirteen generations ago ( c . 1625-1675 ) .