Reachability should check ExtendAllowPrivateAddresses not TestingTorNetwork
It appears that my original fix to bug #13924 (moved) didn't anticipate anyone using "ExtendAllowPrivateAddresses 1" without "TestingTorNetwork 1". I'll submit a patch which swaps TestingTorNetwork for ExtendAllowPrivateAddresses. This will preserve the existing fix, because "TestingTorNetwork 1" implies "ExtendAllowPrivateAddresses 1".
See for more details: https://lists.torproject.org/pipermail/tor-dev/2015-April/008714.html
Credit to CJ Ess for discovering this issue.