You forget bunjab india and pakistan.Another example of ethnicities who don't consider themselves to be one for various reasons.
Tigray speakers consider themselves to be different than Tigray speakers in Ethiopia. They are the same exact people but Eritrean tigrayans would swear they are different and will claim tigrayan Ethiopians stole their history. One key similarity with Somaliland is that the Eritrean Tigray speakers have huge political grievances against Tigray Ethiopians which lead to this different identity. Tigray Ethiopians and Tigrinya speakers in Eritrea speak the same language, have similar culture and the same religion just like Landers and Somalis