Nah 1000 years ago is too early, they were agro pastoralists that migrated from where digil clans lived in modern day eastern Ethiopia to south following wabi ganaale. Maadanle is just one out of the dozen or more Gaala Madow tribes. They're not from Samaale nor were they from the same tribe as him, makes no sense to call them somali out of all the ancient inhabitants of south. Just call them Maadanle that's sufficient.
At least 900 years, that’s according to the linguistic paper when Northern Swahili met Somali. If it wasn’t them, NS has been in direct contact with Somali speakers of the “maay” type for at least a 1000 years ago. IM Lewis collected a similar oral history in the region. When Somalis move, it doesn’t always have be the entire clan- it could have been one section of Tunni or a related group who lived there.
As for Madanle, they were likely a Somali Agro pastoral group who once dominated in Northern Kenya region. Their history is not so ancient, as their decline due to environmental issues and their military defeat by a coalition of other tribes is still remembered. This probably occurred in the Middle Ages. They are at times associated with the Ajuuraan, and they do even appear in their lineages
As for them not being Somali, the region of around Northern Kenya/Southern Somalia was dominated by people similar to Rendilles and other Somalis who adhered to the proto-Somali camel herding culture. The Madanle would have most likely been closely related to these people and interacted with them, hence why Somalis remember them with so much detail and they are the only group who have Madanle in their lineages. Their burial sites are said to be similar to Somalis. Thus, I refer to them as Somali from a genetic, cultural and linguistic perspective.
For the Gaalo madow thing, I believe you are referring to Madanle who were reported to be Gaal Madows around the Badioa area. This could have been the same group or an allied group, we know Agro pastoral groups stretch deep and Develop local alliances. It doesn’t have to mean the ones in Badaio and the ones around Northern Kenya were the same group. Even if we assume they were the same group, the Rendilles are a good example to show Somalis have vastly exaggerated the Gaalo Madow purges reported in their history. Rendilles have many tenants similar to Islam in their culture (praying five times a day etc) which means many of their tribes were formerly Muslim. The Somali peninsula once had folks who were entirely Muslim, some who synchronised Islam With ancient beliefs and those still followed Waaq. The fact that Rendilles till this day have a superstition about killing Somalis as they are “brothers” is an indicator the early Somali Muslim interaction with Somali/east Cushitic non believers was not always one of chasing away the “Gaal Madows”. We have sites bones of pigs alongside Muslim settlements on the Harla sites.
Therefore, the Madanles were very likely a development of the proto Somali- early Somali camel herding and Agro pastoral culture in the region. Separating them form Somalis due to them not having a “Samale lineage” is like saying Boranas and Barentus don’t come form
The same cultural stock (Oromo). Lineages and oral history are just one of facet of understanding and labelling history. It is not the be and end of all of how we understand things. I have no doubt genetic testing will show that Madanle were indistinguishable from “Samales”.