Early Right, what you say has been mentioned a number of times iin different places. (Not sure if it on this thread though).
In fact, it is not correct to say that desert dust is from the same origin as volcanic ash. They are created through completely different processes and have very different qualities. Firstly, dust is generally rounded and smooth and also significanlty larger. This means much less or possibly no erosion and abrasion on surfaces. Also, it is generally accepted that the melting point of dust is much higher than temperatures typically found inside a jet engine, so the threat of melting and deposits forming on turbine sections does not exists.
Volcanic ash is quite unique in that sense. A comparison with dust storms or similar events is not accurate.