`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 (!i2psam_arg.empty()) {
        CService addr;
        if (!Lookup(i2psam_arg, addr, 7656, fNameLookup) || !addr.IsValid()) {
            return InitError(strprintf(_("Invalid -i2psam address or hostname: '%s'"), i2psam_arg));
        }
        SetReachable(NET_I2P, true);
        SetProxy(NET_I2P, proxyType{addr});
    } else {
        SetReachable(NET_I2P, false);
    }
    connOptions.m_i2p_accept_incoming = args.GetBoolArg("-i2pacceptincoming", true);
    if (!node.connman->Start(*node.scheduler, connOptions)) {
        return false;
    }
    
    SetRPCWarmupFinished();
    uiInterface.InitMessage(_("Done loading").translated);
    for (const auto& client : node.chain_clients) {
        client->start(*node.scheduler);
    }
    BanMan* banman = node.banman.get();
    node.scheduler->scheduleEvery([banman]{
        banman->DumpBanlist();
    }, DUMP_BANS_INTERVAL);
#if HAVE_SYSTEM
    StartupNotify(args);
#endif
    return true;
}