They don't care, they just use the most convenient tariff codes because it's less of a hassle pinpointing the exact HTS code for everything we order. For us Americans, I'm fine with them using UPS or even DHL. As long as they do NOT make the switch to FedEx... they are just straight garbage. You guys will not see your jackets/pants/sunglasses for weeks at a time (imagine providing a "Certificate of Origin" from Chamber of Commerce every time you buy something because their workers are so incompetent to interpret international invoices). I'm sure people have had positive experiences but after dealing with them the past few years, I would never use them unless you have an very lucrative discount or you know your clients are extremely patient people.
It also doesn't help that they seem to have a high turnover in the customs clearance department and refuse to hire people who can figure out things by themselves.