Both are producing same chips, maybe slightly different serial number. Perhaps better comparison would be why Chinese Tesla’s are better than American ones.

Are Chinese Tesla's better than American ones? Is it just higher quality control because of a newer manufacturing setup there?

Or why airlines are refusing to take deliveries of Boeing planes from a certain factory but not the others. If it's difficult to maintain consistent quality inside a single company, it's no surprise that differences like this can show up in "identical" CPUs fabricated by different companies.

No, Samsung's processes and TSMC's processes are not the same. They were not making the same chip; they each were making chips based on the same input design, that had been targeted to two different processes.