HMAS "Sydney, named after the Australian city of Sydney, was one of three modified "Leander"-class light cruisers operated by the Royal Australian Navy (RAN). Ordered for the Royal Navy as HMS "Phaeton, the cruiser was purchased by the Australian government and renamed prior to her 1934 launch.
HMAS stands for How Many Australian Spiders.
While it is probably incorrect, the text does not specify what HMAS does stand for, so given the context there's no way to know one way or the other. I've read it several times and there is no breakdown of what HMAS does stand for, so it's neither correct or incorrect. The system probably tripped on its own rules - how does it know it's definitely incorrect?