in v0.12 https://github.com/bitcoin/bitcoin/pull/7081 (by @luke-jr) was merged adding `-bytespersigop` (with default of 20).

this is preventing simple bare multisig transactions from being accepted into mempool when the size is < 400 bytes.  
eg; https://gist.github.com/rubensayshi/ac4f617207f7a50559e85d61c05800be

from 1-of-7 and onwards they are accepted because the ratio of bytes:sigops is high enough.  
also having 2 or more inputs will work because it again tips the ratio of bytes:sigops over.

the reason mainly being that `GetLegacySigOpCount` calls `GetSigOpCount` with `fAccurate=false`.

It looks like changing `GetLegacySigOpCount` to use `fAccurate=true` would cause side effects in the few other places (`ConnectBlock`, `CheckBlock`, `CreateNewBlock`) and simply adding `fAccurate` as arg to `GetLegacySigOpCount` would affect the value stored in `CTxMemPoolEntry.sigOpCount` which in turn affects a bunch of other things.

if (nLocalServices & NODE_WITNESS) {
        
        return;
    }
    if (nodestate->fProvidesHeaderAndIDs) {
        BOOST_FOREACH(const NodeId nodeid, lNodesAnnouncingHeaderAndIDs)
            if (nodeid == pfrom->GetId())
                return;
        bool fAnnounceUsingCMPCTBLOCK = false;
        uint64_t nCMPCTBLOCKVersion = 1;
        if (lNodesAnnouncingHeaderAndIDs.size() >= 3) {
            
            
            CNode* pnodeStop = FindNode(lNodesAnnouncingHeaderAndIDs.front());
            if (pnodeStop) {
                pnodeStop->PushMessage(NetMsgType::SENDCMPCT, fAnnounceUsingCMPCTBLOCK, nCMPCTBLOCKVersion);
                lNodesAnnouncingHeaderAndIDs.pop_front();
            }
        }
        fAnnounceUsingCMPCTBLOCK = true;
        pfrom->PushMessage(NetMsgType::SENDCMPCT, fAnnounceUsingCMPCTBLOCK, nCMPCTBLOCKVersion);
        lNodesAnnouncingHeaderAndIDs.push_back(pfrom->GetId());
    }
}
bool CanDirectFetch(const Consensus::Params &consensusParams)