In a prior version of the Drupal 8 entity API, the idea for language dependent value access was that accessor methods would get a $langcode argument to retrieve specific values in a given language code. The label() method's $langcode argument reflected this thinking. The method would return the label in the given language code.
The final Entity translation API however works with getTranslation($langcode) followed by simple method calls, so variants of the entity can be instantiated and used as if they were the entity itself. Individual $langcode arguments on accessors is therefore pointless and misleading. In fact the label() method's implementation was not even returning the label in the language requested anyway.
Now the $langcode argument (that did not even work) is removed. Use getTranslation() to get a specific translation and access values afterwards.