You’ve pointed out an interesting thing.Honestly I don't think these are being honest about saying they want cadaan woman. Reason being in Somalia even darkskin women if beautiful are chased after regardless of skin tone.
But what I see is that this is just a gender war where divestors are being used to get at the other gender. Somali women will marry an Ajaanib and say she doesn't want Lugo baasto biriq and the men will marry Ajnabi and use that to say they don't want a darkskinned woman. It's just a petty gender war where each side says whatever will make the other side more hurt.
Somali women know many Somali men are insecure about their weight so they cuss them as Lugo baasto. Somali men know that Somali women are sometimes looked down upon as being darkskinned and belittled so they use that insecurity to insult them.