NETINFO cells are used for clock skew checks
In tor-spec.txt, this is outdated:
Implementations MAY use the timestamp value to help decide if their
clocks are skewed. Initiators MAY use "other OR's address" to help
learn which address their connections are originating from, if they do
not know it. [As of 0.2.3.1-alpha, nodes use neither of these values.]