If most tablets don't run ICS or JB, then including that browser in the test could invalidate the overall results for MOST tablet users. Users here on Tech Republic are more likely to root their tablets and not be running the OS approved for it.
Now, I will agree this far. Someone at TechRepublic with a Nexus 7 should run the same tests and provide the results for a JB tablet, which would probably be close to an ICS tablet as well.
-running DRH JB beta on a Viewsonic gTablet
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