Stephen Bolton addressed a similar shortened course issue in 2017 and what Steve wrote then is still correct today. Note that the following 'Golden Rule' speaks of the Tower, but the same applies with any Committee vessel flying the S Flag.
"The Golden Rule for course shortened by the Tower at S Mark;
Always sail between the Tower displaying code flag and Board S and the “S” mark from the direction of the last mark (from the course side)- no matter which mark you’re coming from and no matter what hand course you are sailing.”
As such, to Finish correctly in Saturday's race, boats had to sail between the Tower and S mark leaving S mark to Port.
Results for this race were incorrectly given on Saturday and will be corrected this morning.
Click here to read Steve Bolton's explanatory document discussing the behavior of Code Flag S adjacent to a rounding Mark.
We hope this clears up any confusion.
The Race Committee.