Here are the direct Apple CDN download links for the Safari 16.4.1 update released today (2023-04-07) for macOS Monterey and Big Sur:
Monterey: https://swcdn.apple.com/content/downloads/13/10/032-71505-A_VXEPHZXHA7/cceqmuarwutena64ohro71ydpukpip72i9/Safari16.4.1MontereyAuto.pkg
Big Sur: http://swcdn.apple.com/content/downloads/47/23/032-72735-A_HUFOGBJPRZ/580izn9uc683ima5tc9fykya8lkbhkji4t/Safari16.4.1BigSurAuto.pkg
The macOS Ventura 13.3.1 update contains the Safari 16.4.1 update for macOS Ventura, and there is no standalone updater for it.