But expatinown country, could they not just allow the offical rate to devalue, which would arguably increase exports and thus increase dollars coming in to the country given the exporters still have to convert their dollars at official rate (its law anyway). Then, if the official rate decreases, potentially it would decrease demand from purchases etc abroad and thus they wouldnt be losing dollars from that aspect.
Or, have they done the maths (wouldnt surprise me if not you know) and it works out better this way, having them being able to buy the dollars at the lower official rate given the proportion of exports denominated in USD (soya, girasol et al).