That wording that you bolded is nearly unattainable, as there are very few (if any) intl-to-intl connections you can make in Urumqi that are within 2 hours. The most common west-east connection is China Southern doing Intl +URC + CAN + Intl combo. But, no confirmation available and no guarantees. If you want the sure bet, pay up and get a visa in advance. However, given your particulars, I believe you will be fine on this double-stop transit without a Chinese visa if you are obviously European and not of Turkish/ Middle Eastern name or appearance. One thing that might help is getting that Vietnamese e-visa in advance, so that you have proof of admissability to your ultimate destination after China before you start the journey. Better than telling check-in staff you expect to VOA in Vietnam.