Firmware / software updates like this get rolled out in phases and depend on the phone version, lock status, etc.
Security updates typically happen early in the month but aren't guaranteed by a certain date, after all testing and verifying quality may take more time if an issue is found.
Since no one wants bugs in their software updates, I'd encourage you to keep checking and be patient for updates like this.
Based off this article I'd bet it's coming soon! https://www.sammobile.com/news/august-2020-security-update-galaxy-s20-unlocked-snapdragon-us