Earlier quoted context omitted.
CSV is not a standard (rfc4180 exists but only very few things actually pay attention to it) so no behavior is a sane behavior when trying to import it.
You sound like a C compiler. "This is technically undefined behavior so whatever" is not a useful guiding principle for user interfaces.
In almost all situations where one could use CSV, a better, more structured, more standards-compliant, more optimized file format (like a SQLite database) would be a better choice.