https://github.com/ibexa/core/blob/3e143a0eb6ecee0aba610728c7a9dfa79b637556/src/lib/FieldType/Unindexed.php#L14 incorrectly claims that \Ibexa\Core\FieldType\Unindexed is the "Indexable definition for string field type".

Additionally, the docblock of the default field getter methods only says that these methods return a string (also see \Ibexa\Contracts\Core\FieldType\Indexable), while they return null in this class.