AFAICT, as of commit a0a422c,  we have 2 different logics to evict outbound peers : lagging-chain (`ConsiderEviction`) and (`CheckForStaleTipAndEvictPeers`). The former to sanitize out lazy/buggy peers who have never sent us a valid header and are always staying behind our tip, the latter triggered in case of stale tip due to block variance to seek a better chain by rotating our outbound peers if we already reach an outbound limit (`EvictExtraOutboundPeers`).

Block-relay-only peers were introduced by #15719. Contrary to outbound full-relay peers who provided us at least a useful header, they're not protected by lagging-chain eviction.

We actually have a comment inside `ProcessHeadersMessage` indicating the contrary behavior. We should either document cleanly that block-relay-only aren't protected or effectively extend the scope of protection to them.

Hinted during #19724 review, see https://github.com/bitcoin/bitcoin/pull/19724#discussion_r475144532
Misbehaving(pfrom.GetId(), 20, strprintf("headers message size = %u", nCount));
            return;
        }
        headers.resize(nCount);
        for (unsigned int n = 0; n < nCount; n++) {
            vRecv >> headers[n];
            ReadCompactSize(vRecv); 
        }
        return ProcessHeadersMessage(pfrom, headers, false);
    }
    if (msg_type == NetMsgType::BLOCK)
    {
        
        if (fImporting || fReindex) {
            LogPrint(BCLog::NET, "Unexpected block message received from peer %d\n", pfrom.GetId());
            return;
        }
        std::shared_ptr<CBlock> pblock = std::make_shared<CBlock>();
        vRecv >> *pblock;
        LogPrint(BCLog::NET, "received block %s peer=%d\n", pblock->GetHash().ToString(), pfrom.GetId());
        bool forceProcessing = false;
        const uint256 hash(pblock->GetHash());
        {
            LOCK(cs_main);
            
            
            forceProcessing |= MarkBlockAsReceived(hash);