The Frequently Visited section on the default home page does not show any entries in Release 171. I the previous release, the Frequently Visited section was populated and shown. This also seems to manifest in the address bar not offering previously visited / entered URL's. I have to completely enter any URL that used to be in the Frequent Visited section.
<rdar://problem/110745781>
This sounds like a Safari bug rather than something that can be fixed via WebKit open source changes. Please file a bug via feedbackassistant.apple.com and include a sysdiagnose.
Reported. #FB12348889