Any stainless could be used for an exhaust so it would depend on what grade and alloy they decided to use. As typical, the cheaper parts will use a low grade stainless. That stuff is only a bit resistant to rust, that's all. Even the high end stuff can and will rust but it takes far longer.Maybe go OBX headers / cat back for non sky engines. I tend to try to stay away from china made stainless.
I installed a china made stainless steel high flow cat from Yonaka and exterior is already rusty red/rose looking compared to the Corksport stainless exhaust
and MSDS headers ... both look brand new after 3 years. Not sure if stainless cat is a same stainless steel on exhaust components
The rust resistance is a function of how much chromium is in that alloy. In the future you could always ask the seller the stainless grade and do your own research....if you trust them to be honest
The structural requirements of an exhaust pipe or cat are pretty well nothing besides the heat cycling. Any steel should be ductile enough to handle that heat. I'd be only concerned with the chromium content.
Thing is...that chromium costs