My summary of this blog post: plenty of random input data can reveal code bugs. The kind of bugs that would take probably a lot of time of think of and write unit tests for, in advance.
Would it? Maybe it's because I've had a "low-level upbringing", but whenever I'm writing parsing code for a file format, "assume any byte of data you read can have any value" is the norm. The rest of it follows from there.
But when the result is more than 10, you've wrapped: your answer is off the D scale. So now you have to push the inner part back to the left, and line up the 10 (usually marked as 1, at the right-hand end) on the C scale with the first number on the D scale. And remember to add 1 to the exponent.
I've seen slide rules where the D scale goes slightly beyond 10 (like 10.1), so if the result was just a tiny bit over 10, you wouldn't need to wrap.