`RewindBlockIndex` was made to allow nodes upgrading to new consensus rules post-segwit fork to 
download new consensus data (i.e witnesses) without having to go through a whole IBD. It has been pointed than now really few pre-segwit nodes care to upgrade and that this logic may be irrelevant.

See https://github.com/bitcoin/bitcoin/pull/17737#discussion_r358514335 in review  of #17737 for more context pointers.
}
            } while (!m_chain.Tip() || (starting_tip && CBlockIndexWorkComparator()(m_chain.Tip(), starting_tip)));
            if (!blocks_connected) return true;
            const CBlockIndex* pindexFork = m_chain.FindFork(starting_tip);
            bool fInitialDownload = IsInitialBlockDownload();
            
            
            if (pindexFork != pindexNewTip) {
                
                GetMainSignals().UpdatedBlockTip(pindexNewTip, pindexFork, fInitialDownload);
                
                uiInterface.NotifyBlockTip(GetSynchronizationState(fInitialDownload), pindexNewTip);
            }
        }
        
        if (nStopAtHeight && pindexNewTip && pindexNewTip->nHeight >= nStopAtHeight) StartShutdown();
        
        
        
        
        if (ShutdownRequested()) break;
    } while (pindexNewTip != pindexMostWork);
    CheckBlockIndex(chainparams.GetConsensus());
    
    if (!FlushStateToDisk(chainparams, state, FlushStateMode::PERIODIC)) {
        return false;
    }
    return true;
}
bool CChainState::PreciousBlock(BlockValidationState& state, const CChainParams& params, CBlockIndex *pindex)