Going by what I have witnessed, and anecdotes - not only by some boaters, but professional fisherman, tool manufacturers, and other parts suppliers - Chinese made products using Stainless Steel have more tarnishing issues. A friend is a sportfisher captain working a 90' charter, a professional fisherman - he pulls apart the reels for maintenance and the ones produced in China have rust on the stainless. These are high dollar reels mind you.
Might be that the yard sourced the stainless from a less reputable producer, or a vendor was called in to fab the rails and they choose a lower quality SS, or a less reputable vendor for their parts.
Could this happen in Taiwan, or Turkey - yes, but I have specific and anecdotal evidence of it in China.
That, and unless you haven't been following the news, I'd rather as few dollars go to China as possible. Part of my personal ESG.
Buying anything new from China also carries a Tariff. My recommendation to any manufacturer is setup shop elsewhere.
But my point is that stainless on boats produced in Turkey and in much of Europe comes from China. You don't escape it by not buying a Chinese boat. I could name a British and an Italian brand with horrible stainless, from China.
And, yes, quality varies by producer, even among Chinese metal manufacturers. I'm just pointing out that you face the same issue with boats built throughout Europe.