I opted out of beta downloads under System Preferences > App Store, but I still see macOS beta downloads in the Mac App Store.
How can I fix this? Caching issue?
From:
https://discussions.apple.com/message/30929430#30929430
Once you've unenrolled, run this command in the terminal:
sudo softwareupdate --clear-catalog
This worked for me!
Once you unenroll in System Preferences, beta updates will still appear until the next commercial release of the software that you opted-in for (macOS or iOS). At that time, you can upgrade to the stable commercial release and you will no longer receive beta notifications.
If you further wish to leave the beta program entirely, after unenrolling in System Preferences go to the Apple Beta unenroll page and click the link at the very bottom of the page.