`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.
assert(coins.GetBestBlock() == pindex->GetBlockHash());
            DisconnectResult res = active_chainstate.DisconnectBlock(block, pindex, coins);
            if (res == DISCONNECT_FAILED) {
                return error("VerifyDB(): *** irrecoverable inconsistency in block data at %d, hash=%s", pindex->nHeight, pindex->GetBlockHash().ToString());
            }
            if (res == DISCONNECT_UNCLEAN) {
                nGoodTransactions = 0;
                pindexFailure = pindex;
            } else {
                nGoodTransactions += block.vtx.size();
            }
        }
        if (ShutdownRequested()) return true;
    }
    if (pindexFailure)
        return error("VerifyDB(): *** coin database inconsistencies found (last %i blocks, %i good transactions before that)\n", active_chainstate.m_chain.Height() - pindexFailure->nHeight + 1, nGoodTransactions);
    
    int block_count = active_chainstate.m_chain.Height() - pindex->nHeight;
    
    if (nCheckLevel >= 4) {
        while (pindex != active_chainstate.m_chain.Tip()) {
            const int percentageDone = std::max(1, std::min(99, 100 - (int)(((double)(active_chainstate.m_chain.Height() - pindex->nHeight)) / (double)nCheckDepth * 50)));
            if (reportDone < percentageDone/10) {
                
                LogPrintf("[%d%%]...", percentageDone); 
                reportDone = percentageDone/10;
            }
            uiInterface.ShowProgress(_("Verifying blocks...").translated, percentageDone, false);
            pindex = active_chainstate.m_chain.Next(pindex);
            CBlock block;