This is what I've heard from some people. Unverified and may just be hearsay, but somehow it sort of makes sense.
China is practising a form of 'genocide' (don't know if there is a better term for what I am about to share). But instead of openly murdering people, they are sending hordes of Hans to mix with the Uyghurs in Xinjiang. The Hans are 'encouraged' to live with the Uyghurs, brainwash them to tow the CCP line and, ultimately marry and start a family with them. This way, it will dilute the Uyghurs' genes, culture, identity etc. to a point where Uyghurs will simply cease to exist in the future.
Maybe this is why they want them back in China - they do not want even one to be spared of this 'conversion'. Maybe this is just another conspiracy theory, I don't know. Just sharing.