`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.
fInvalidFound = true;
                    fContinue = false;
                    break;
                } else {
                    
                    
                    
                    UpdateMempoolForReorg(*this, m_mempool, disconnectpool, false);
                    return false;
                }
            } else {
                PruneBlockIndexCandidates();
                if (!pindexOldTip || m_chain.Tip()->nChainWork > pindexOldTip->nChainWork) {
                    
                    fContinue = false;
                    break;
                }
            }
        }
    }
    if (fBlocksDisconnected) {
        
        
        UpdateMempoolForReorg(*this, m_mempool, disconnectpool, true);
    }
    m_mempool.check(*this);
    CheckForkWarningConditions();
    return true;
}
static SynchronizationState GetSynchronizationState(bool init)