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
static size_t vExtraTxnForCompactIt GUARDED_BY(g_cs_orphans) = 0;
} 
namespace {
/**
 * Maintain validation-specific state about nodes, protected by cs_main, instead
 * by CNode's own locks. This simplifies asynchronous operation, where
 * processing of incoming data is done after the ProcessMessage call returns,
 * and we're no longer holding the node's locks.
 */
struct CNodeState {
    
    const CService address;
    
    bool fCurrentlyConnected;
    
    const CBlockIndex *pindexBestKnownBlock;
    
    uint256 hashLastUnknownBlock;
    
    const CBlockIndex *pindexLastCommonBlock;
    
    const CBlockIndex *pindexBestHeaderSent;
    
    int nUnconnectingHeaders;
    
    bool fSyncStarted;
    
    int64_t nHeadersSyncTimeout;
    
    int64_t nStallingSince;