I can't recall any study which found what I would call "high" levels of R in Uyghur populations. There is some, of course, but it should be the responsibility of Eupedia or - especially - Wikipedia to provide a source for their assertion.
I think maybe some of it goes back to this map
, which does have a bibliography on page 4.
Its pie chart for the Uyghurs shows about 30-40% or so R1, split nearly evenly between R1a and R1b, but I'm not sure which study on the list on page 4 was the source for that particular pie chart.