The FRHIFrameFlipTrackingRunnable thread is not initialized on Windows, so RHIGetFrameRate always returns zero.
As a workaround, remove the code added by CalculateFPSTimings for Windows platform, and 5.0 behavior will be restored.
if (CVarGTSyncType->GetInt() == 2 && CVarVsync->GetInt() ! = 0).
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-176105 in the post.