Best answer by ratty
All you see there is for Sonos internal use only, and is undocumented, but we've figured out a few things over the years.
The main application log is at /opt/log/anacapa.trace. Timestamps use the offset internal clock.
The Linux system log is at /bin/dmesg. Timestamps are seconds from boot.,
Of potential interest is the RF information at /proc/ath_rincon/status, though the Network Matrix provides this in a more concise and digestible format. If the system isn't in SonosNet mode (aka 'BOOST Setup') then the matrix is meaningless.
/proc/ath_rincon/phyerr is a histogram of physical errors on the RF over the last 20 minutes.