Wiki says they’re still 94% Icelandic, kinda shit source, but I don’t think they’d go massively African in a couple years skewing the results so heavily. I’d argue it’s poor sample selection or something. Ultimately it’d require dna comparison between Icelanders and peoples from the Nordic states. Maybe throw in some older Nord dna to see if they were lactose and it was like Germanic admixture that increased the modern Nord peoples to have a higher tolerance to milk I dunno