Symmetric Key Creation Question
I believe you are correct and the docs need updating.  Should probably read:


  When a symmetric key is encrypted with a password instead of a
  certificate (or another key), the TRIPLE DES encryption algorithm is
  used to encrypt the password. Because of this, keys that are created
  with a strong encryption algorithm, such as AES, are themselves
  secured by a weaker algorithm.


docs.microsoft.com is all on GitHub, so you can propose doc changes.

I've submitted a pull request to update the language.  You can follow it here: https://github.com/MicrosoftDocs/sql-docs/pull/310