Verifiers with minAgeSec == 0 (finalized mode) will perform the state verification based on finalized nodes/blocks. However, OPVerifiers finalized mode incorrectly uses the latest proposed nodes, which are not finalized yet.
That is because OP (pre-FaultProof version) has a finalizationPeriodSeconds field that defines the Number of seconds that a proposal must be available to challenge before it is considered finalized by the OptimismPortal contract. as stated in the docs.
This is exposed as a getter isOutputFinalized() in OptimismPortal.sol#L421-L428, and is also utilized when finalizing withdrawals.
In the code below, we can see that getLatestContext() uses the latest proposed output node from latestOutputIndex() when minAgeSec == 0. As OP block time is 2 seconds, the latest output node is unfinalized as it would not have passed the finalization period (typically 7 days).
In addition, getStorageValues() does not ensure that the output node given by the gateway is finalized, when p.outputIndex != outputIndex1.
Update OPVerifier to perform the following when minAgeSec == 0,
Fixed here.
[M-01] has been resolved utilising a Game Finder approach (OPOutputFinder) similar to that used in the OPFaultVerifier. This facilitates an efficient search of submitted outputs giving consideration to both finalised and unfinalised Gateway/Verifier operation. It also minimises the need for excessive RPC calls within the Javascript implementation.
Resolved with a new OPOutputFinder for OPVerifier, which will search for the latest node with timestamp <= minAgeSec. For minAgeSec == 0, it uses oracle.finalizationPeriodSeconds(), which is essentially searching for the latest finalized node.
Note: for finalized mode, OPVerifier.getStorageValues() does not need an explicit check to check the gateway provided node is finalized, as it relies on _checkWindow() to reject unfinalized nodes. _checkWindow() will reject nodes after latest finalized node, which are by definition unfinalized. In addition, in OP (pre-FaultGame), rejected nodes are deleted so nodes older than the latest finalized node are always finalized. 
