I have two conflicting views in this issue:
1) In favor:
Xīnjiāng, as you mentioned, issued distinctive coinage. In addition, Xīnjiāng was an independent (unrecognized) state for a couple of years (as "East Turkistan"). Many of the coins of Xīnjiāng are quite different from their Chinese counterparts and used Turkic denominations.
2) Against:
Xīnjiāng spent a lot of time under Chinese rule (most of its coin-issuing history). Its coins were often similar to Chinese coins. Xīnjiāng in this respect is different from Hong Kong, Macau, and Tibet (its counterpart in many ways). All three of these spent a lot of time independent from China (although Tibet was a tributary state for a long time) and issued very distinctive coinage. Even when Xīnjiāng was independent, "East Turkistan" only really existed in Kashgar and the immediate vicinity. In addition, many coins from Xīnjiāng are indistinguishable from their Chinese counterparts for someone who cannot read the inscriptions (and even then, look like regular Chinese provincial coinage).
This will certainly be an issue to settle, and I will disagree with you as my final decision, but both arguments are very valid. Please keep in mind that there was also a Uighur Kahnate at some point although I'm not sure about the status of its coins.