It certainly isn't; it's killed by SIGPIPE after printing 50 lines. If I wanted to wait for the entire system log to read off of disk I'd be sitting for minutes

It certainly isn't; it's killed by SIGPIPE after printing 50 lines. If I wanted to wait for the entire system log to read off of disk I'd be sitting for minutes. "journalctl -r -n 50" takes 5.4 seconds as of a test just now from (this time, artificially) cold cache.