http://manuals.info.apple.com/enUS/EnterpriseDeployment_Guide.pdf

which says:

If you’re using both device policies and Exchange passcode policies, the two sets of policies are merged and the strictest of the settings is enforced.

and a bit later, the part which says that an Exchange administrator can set the value to something less than 10, and the consequences:

Maximum number of failed attempts: The value you select determines how many failed passcode attempts can be made before the device is wiped. By default, after six failed passcode attempts, the device imposes a time delay before a passcode can be entered again. The time delay increases with each failed attempt. After the eleventh failed attempt, all data and settings are securely erased from the device. The passcode time delays always begin after the sixth attempt, so if you set this value to 6 or lower, no time delays are imposed and the device is erased when the attempt value is exceeded. You cannot specify a value greater than 11—the device always wipes its data if the user fails to enter the correct passcode 11 times in a row.

I read the same deployment guide just after the release of the 2.0 software, so this feature of wiping the device after n failures (where n is configurable by the Exchange admin) has always been there in 2.0. The only new feature in 2.1 is that the setting is now exposed to non-Exchange users.

The screenshot in the article showing the 5 attempt case is clearly that of an Exchange user, because "Erase all data" is grayed out (the policy that Exchange admin created doesn't allow changing the setting). For non-Exchange users of 2.1, this setting is changeable.

Nothing to see here folks, move along. Jeremy, please fix the article.

Our Windows Mobile devices also only have 5 attempts. 10 is the default setting if no policies are enforced.