Looks like Harley switched to smooth cylinders for the rear mounting points mid-2024, which is why the holes are unthreaded. Some riders have tapped the holes or used thread inserts, but it's a bit of a DIY fix. If you're up for it, you can try that, but I'd double-check with your dealer to avoid any warranty issues.
For a visual guide on top rack installation, you might find this video helpful: