The grammars in rule-based MT are normally fully conceptually understood by the people who wrote them. That's a good start for human understanding.
You could say they don't understand why a human language evolved some feature but they fully understand the details of that feature in human conceptual terms.
I agree in principle the statistical parts of statistical MT are not secret and that computer code in high-level languages isn't guaranteed to be comprehensible to a human reader. Or in general, binary code isn't guaranteed to be incomprehensible and source code isn't guaranteed to be comprehensible.
But for MT, the hand-written grammars and rules are at least comprehended by their authors at the time they're initially constructed.
You could say they don't understand why a human language evolved some feature but they fully understand the details of that feature in human conceptual terms.
I agree in principle the statistical parts of statistical MT are not secret and that computer code in high-level languages isn't guaranteed to be comprehensible to a human reader. Or in general, binary code isn't guaranteed to be incomprehensible and source code isn't guaranteed to be comprehensible.
But for MT, the hand-written grammars and rules are at least comprehended by their authors at the time they're initially constructed.