It looks like Mozilla changed the System Requirements for Firefox between version 78.x and 79.0. Firefox 79.0 requires macOS 10.12 or newer. Firefox 78.0 required macOS 10.9 or newer. The 79.0 patch definition from Jamf does not reflect this change.

I added an exclusion to the scope to prevent it from being served up to my 10.9 to 10.11 stragglers, but it would be preferable to have the requirements addressed in the definition.