`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 (coinstip_size == m_coinstip_cache_size_bytes &&
            coinsdb_size == m_coinsdb_cache_size_bytes) {
        
        return true;
    }
    size_t old_coinstip_size = m_coinstip_cache_size_bytes;
    m_coinstip_cache_size_bytes = coinstip_size;
    m_coinsdb_cache_size_bytes = coinsdb_size;
    CoinsDB().ResizeCache(coinsdb_size);
    LogPrintf("[%s] resized coinsdb cache to %.1f MiB\n",
        this->ToString(), coinsdb_size * (1.0 / 1024 / 1024));
    LogPrintf("[%s] resized coinstip cache to %.1f MiB\n",
        this->ToString(), coinstip_size * (1.0 / 1024 / 1024));
    BlockValidationState state;
    const CChainParams& chainparams = Params();
    bool ret;
    if (coinstip_size > old_coinstip_size) {
        
        ret = FlushStateToDisk(chainparams, state, FlushStateMode::IF_NEEDED);
    } else {
        
        ret = FlushStateToDisk(chainparams, state, FlushStateMode::ALWAYS);
        CoinsTip().ReallocateCache();
    }
    return ret;
}
std::string CBlockFileInfo::ToString() const