Yeah, Oromo is the closest language to Somali and yet it is completely unintelligible to me.
That shouldn’t come as surprise as some Somali dialects like Af Maay and Jiddu are sometimes unintelligible to Af Maxa Tiri speakers. Oromo and Somali have been isolated from each other for thousands of years after the earlier Cushitic splits.
From the clips Awale of Anthro madness posted on YouTube, Rendille sounds more intelligible to a Somali speaker.