I can't master how to "insert spoiler", but I'm guessing that the tie is specific to the (yachting?) organisation that he was visiting, so fair dos, even if a plain shirt would have been better.
What strikes me (and HRH The Prince of Wales is at an intermediate or transitional stage) is how Royals have stopped dressing conspicuously and now dress very conventionally. Best example being Prince W's wedding night dinner jacket with black brogues. Exactly what their contemporaries from school or Sandhurst would wear, whether or not SF would approve.