I had borosilicate (brand name) thin laboratory glassware be effected by thermal shock, I don't think its completely immune, more like there is a probability that something will happen and its reduced with quartz, its likely just a better higher durability material they specified.
Solder is different then a flame also, because a flame is fairly mellow, solder will splatter on the glass randomly with random sizes as its being sucked in and have a extremely high thermal transfer rate along the random interface.