Whole Europe will usually be released at the same time. Last year the sale date was one week earlier for the Southampton based cruises, than the Mediterranean ones.
https://www.princess.com/en-int/news/news-releases/2023/05/new-star-princess-and-sun-princess-headline-2025-europe-cruises-and-cruisetours-season-as-princess-cruises-celebrates-40th-anniversary-sailing-in-the-mediterranean