Well, I don't know the study, but if this Yoruba is modern, as I think it is, then it could be a mere case of redundancy, in which modern Yoruba would logically prefer modern Yoruba over other pops, since they're the reference for themselves.
That said, Yoruba does have some Eurasian ancestry, as evidenced by Lazaridis et al. It would be something around 5% of WHG-related ancestry, via Dzudzuana, in turn via ~13% of Taforalt-related ancestry. This finding is reinforced by the fact Yoruba also has a bit of Neandertal ancestry.
https://www.biorxiv.org/content/biorxiv/suppl/2018/09/20/423079.DC1/423079-1.pdf
Lazaridis et al. also used modern Yoruba (bold always mine):
"We sought to determine the direction of admixture without a priori assumptions by forming the following set, which includes All plus a ~2,000BP hunter-gatherer from South Africa20, a ~4,500 year old sample from East Africa (Mota),
Yoruba (from present-day West Africa where no ancient genomic data is available), Taforalt and Natufians:"
But they would have worked data differently, and they corrected a previous finding of SSA supposedly contributing to Taforalt:
"The study of the Ibero-Maurusian remains from Taforalt was initially interpreted as suggesting that this population was formed by admixture between Natufians and a Sub-Saharan population15. However, the admixture graph model suggests the opposite scenario: that Natufians were formed by admixture from a Taforalt-related population and a Dzudzuana-related one."
Also:
"The results of our analysis using the All set, as well as the results of the analysis of ref.15 do suggest that Taforalt can be modeled as a mixture of a West Eurasian related population (represented by Dzudzuana in our case) and a Sub-Saharan African lineage. However, when one uses only a single African population as a source without using others as outgroups, this mixture can only be interpreted as evidence of ancestry from a lineage basal to members of the All set, rather than as evidence of ancestry specifically related to the chosen African population. No Sub-Saharan African populations appear to be good sources for the ancestry of Taforalt as described previously. The admixture graph model suggests an alternative possibility: that it is West African populations like the Yoruba that may have ancestry from a North African Taforalt-like population. Under such a scenario, North Africa and the Levant were occupied by populations that experienced gene flow from each other, with more ancestry from a Basal lineage in North Africa, and more ancestry from a West Eurasian-specific lineage (represented by Dzudzuana) in the Levant, thus explaining the presence of Dzudzuana-related admixture in Taforalt and of Taforalt-related admixture in the Levant.
Under this scenario, a North African-related population may have contributed some ancestry to Sub-Saharan populations to its south, perhaps during the Holocene Green Sahara period (~11-6kya)22 that postdates the sampled Taforalt individual which may have facilitated north→south gene flow across the Sahara."
Fortunately, we already have now two 8k years old samples from Cameroon.
https://www.nature.com/articles/s41586-020-1929-1
I don't know when this flow South of Taforalt-related ancestry started, but modern Yoruba do score some Taforalt in G25, in a model using as sources these two ancient SSA and also Taforalt.
