The submission actually states (correctly): "UCS-2 can only represent the first 65536 characters of Unicode, also known as the Basic Multilingual Plane." UTF-1

The submission actually states (correctly): "UCS-2 can only represent the first 65536 characters of Unicode, also known as the Basic Multilingual Plane." UTF-16 can represent all Unicode code points, through surrogate pairs when needed. Systems that originally were designed for UCS-2 have often been upgraded to UTF-16. E.g. Windows, JS. But it is then not UCS-2 anymore. In some case the documentation and/or function names, etc., might talk incorrectly about being UCS-2 (while they really are UTF-16 now) for historical reasons, adding to the confusion.