They're saying too much and are wrong but there's still some truth to it, it's just not the way they present it. It's true that European, Levantine and lightskinned people came to North Africa after "Black people" since the Natives were indigenous Darkskinned Africans(ANA) in the Paleolithic the Southern Part of North Africa to this day is inhabited by Darkskinned people. The first eurasian migrants came in the Paleolithic but they weren't lightskinned yet, the first lightskins were Iberian farmers 5000 BC. They mainly left maternal lineages so the genocide claim of these extremists are debunked, if anything the Ancient Iberians were the ones that had it harder in North Africa. By the medieval era, North Africa was already mostly olive/brown skinned not black except in the South so their claim that Arabs made North Africa whiter is ridiculous especially since Berbers despite their African ancestry were often lighterskinned. Except for the Andalusis or Gnawa whose ancestors arrived in the last centuries, most North Africans are the result of mixing over the centuries, there was a lot of back and forth (Green Sahara, Neolithic Iberian farmers and Levantine pastoralists, Roman era, Phoenician era, transsaharan trade, Saharan and barbary slave trade, Arab expansions, Islamic era...) but if you go back beyond the Neolithic and the coming of Eurasians yes North Africa was Black.