-> And i've found the release (instead of RC) version; your link https://winscp.net/eng/downloads.php#stable_portablezip does scroll to RC version - and i didn't saw that. i lil bit of scrolling above and i got it.. ;-)
It scrolls to "Portable executables" of WinSCP 5.17. At least for me – Tested on all major browsers. Can you check again and post a screenshot if it still does not work for you correctly?