According to Apple Safari 11.0.2 is “Available for: OS X El Capitan 10.11.6 and macOS Sierra 10.12.6”
The relevance in the fixlet is: (exists string “ProductVersion” whose (it as string = “10.12”) of dictionary of it) of file “/System/Library/CoreServices/SystemVersion.plist”
That relevance does not reflect 10.12.6, the 10.11.6 version of the fixlet has the proper relevance: (exists string “ProductVersion” whose (it as string = “10.11.6”) of dictionary of it) of file “/System/Library/CoreServices/SystemVersion.plist”