`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.
int maxInputHeight = 0;
            for (const int height : prevheights) {
                
                if (height != tip->nHeight+1) {
                    maxInputHeight = std::max(maxInputHeight, height);
                }
            }
            lp->maxInputBlock = tip->GetAncestor(maxInputHeight);
        }
    }
    return EvaluateSequenceLocks(index, lockPair);
}
static unsigned int GetBlockScriptFlags(const CBlockIndex* pindex, const Consensus::Params& chainparams);
static void LimitMempoolSize(CTxMemPool& pool, CCoinsViewCache& coins_cache, size_t limit, std::chrono::seconds age)
    EXCLUSIVE_LOCKS_REQUIRED(pool.cs, ::cs_main)
{
    int expired = pool.Expire(GetTime<std::chrono::seconds>() - age);
    if (expired != 0) {
        LogPrint(BCLog::MEMPOOL, "Expired %i transactions from the memory pool\n", expired);
    }
    std::vector<COutPoint> vNoSpendsRemaining;
    pool.TrimToSize(limit, &vNoSpendsRemaining);
    assert(std::addressof(::ChainstateActive().CoinsTip()) == std::addressof(coins_cache));
    for (const COutPoint& removed : vNoSpendsRemaining)
        coins_cache.Uncache(removed);
}
static bool IsCurrentForFeeEstimation(CChainState& active_chainstate) EXCLUSIVE_LOCKS_REQUIRED(cs_main)