`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 (nSigOpsCost > MAX_STANDARD_TX_SIGOPS_COST)
        return state.Invalid(TxValidationResult::TX_NOT_STANDARD, "bad-txns-too-many-sigops",
                strprintf("%d", nSigOpsCost));
    
    
    if (!bypass_limits && !CheckFeeRate(nSize, nModifiedFees, state)) return false;
    const CTxMemPool::setEntries setIterConflicting = m_pool.GetIterSet(setConflicts);
    
    if (setConflicts.size() == 1) {