From the article: >>>The Problem: Even if the reader detects that the data was modified and discards the copy before use, the act of copying the non-atomic data itself still triggers undefined behavior. While a sequence lock can detect that a data race occurred, it does not prevent it.

Why is this a problem? Isn't the correct way to deal with a sequence lock failure to just retry? A torn read yes means you get undefined behavior as far as the result of your read, but you throw it all away and start again anyway so what is this solving?

From a hardware perspective this is correct. From a language perspective it's UB, and unless your compiler has defined that UB, it doesn't matter what the hardware's behavior is unless you're writing assembly.