I agree with your conclusion. People are buying NxT at a premium (rushing) to trade for NEM, this has an upswing effect on NxT. As we are seeing now, as volume declines for NEM (went from 4 million to 3.5 million), this coincides with a decrease in NxT value as the number of people looking to buy on premium is on the decline at the moment.
Here is amount of AE volume in last 30 days
http://www.cryptoassetcharts.info/assets/infoAs you can see there a lot of other assets that had big volume (bigger or just as big) as Nem