macOS system report's installation does not list all software installations

The listing comes from /Library/Receipts. In current macOS systems, it's in the file InstallHistory.plist. Formerly, there were separate receipt files for each installed item.

Receipts are created by applications and other files installed from installer packages (.pkg files) via macOS' Installer utility (see man installer in the Terminal for more info), and those installed by the Mac App Store and Software Update. Applications that are simply dragged into the Applications folder (as is the case with EaseUS Data Reovery) don't create receipts. Some applications, like Little Snitch, may use customized installer applications that likewise don't create receipts.