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
mapBlockSource.emplace(hash, std::make_pair(pfrom.GetId(), true));
        }
        bool fNewBlock = false;
        m_chainman.ProcessNewBlock(m_chainparams, pblock, forceProcessing, &fNewBlock);
        if (fNewBlock) {
            pfrom.nLastBlockTime = GetTime();
        } else {
            LOCK(cs_main);
            mapBlockSource.erase(pblock->GetHash());
        }
        return;
    }
    if (msg_type == NetMsgType::GETADDR) {
        
        
        
        
        
        if (!pfrom.IsInboundConn()) {
            LogPrint(BCLog::NET, "Ignoring \"getaddr\" from %s connection. peer=%d\n", pfrom.ConnectionTypeAsString(), pfrom.GetId());
            return;
        }
        
        
        if (pfrom.fSentAddr) {
            LogPrint(BCLog::NET, "Ignoring repeated \"getaddr\". peer=%d\n", pfrom.GetId());
            return;
        }
        pfrom.fSentAddr = true;
        pfrom.vAddrToSend.clear();