`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.
if (ShutdownRequested()) {
        LogPrintf("Shutdown requested. Exiting.\n");
        return false;
    }
    
    if (args.GetBoolArg("-txindex", DEFAULT_TXINDEX)) {
        g_txindex = std::make_unique<TxIndex>(nTxIndexCache, false, fReindex);
        g_txindex->Start();
    }
    for (const auto& filter_type : g_enabled_filter_types) {
        InitBlockFilterIndex(filter_type, filter_index_cache, false, fReindex);
        GetBlockFilterIndex(filter_type)->Start();
    }
    
    for (const auto& client : node.chain_clients) {
        if (!client->load()) {
            return false;
        }
    }
    
    
    
    if (fPruneMode) {
        LogPrintf("Unsetting NODE_NETWORK on prune mode\n");
        nLocalServices = ServiceFlags(nLocalServices & ~NODE_NETWORK);
        if (!fReindex) {
            LOCK(cs_main);