Charles is King of Scotland separately from being King of England and Wales, The two kingdoms together make up the United Kingdom, and have done since 1603 when Queen Elizabeth 1 of England died without an heir and the throne went to her near nearest relative, Charles VI of Scotland (and Charles I of England)
If the shoe had been on the other foot and C Rex 3 had been crowned in Scotland without being crowned in England, there would have been one hell of a stushie in England, and people would have insisted on a Wesrminster coronation before he was considered legitimately king.
Imbalance?