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The 2AZ-FE engine in that Camry has only a 9.6:1 compression ratio, which is pretty low. It shouldn't be anywhere near knock limited even on 87 octane.
The hybrid version of the engine has a 12.5:1 compression ratio which could easily benefit from higher octane fuel if that were the end of the story, but I'm nearly certain it doesn't have ignition timing tables for higher octane fuel, and those improvements would really only apply at wide open throttle anyway. Instead the hybrid runs the Atkinson cycle to reduce the dynamic cylinder pressure, which again makes low octane fuel perfectly fine to run.
91 should not be called "supreme" or "ultra" as it does absolutely nothing in engines not designed specifically to run on them, and those engines typically don't run at all on lower octane fuels.
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