socklog-unix runs svlogd like this:

svlogd \
  main/main main/auth main/cron main/daemon main/debug main/ftp \
  main/kern main/local main/mail main/news main/syslog main/user

There is no svlogd config file, so I expect all message to go to all
logs.  What I see instead is some kind of implicit splitting among the
log files.

This behavior isn't documented on the svlogd man page (runit 1.3.2-1
debian).  So how does it work?