Here’s another example of how Apple’s application approval process for the iPhone doesn’t make sense. One of the big rules is that Apple (NSDQ: AAPL) doesn’t allow companies to use undocumented APIs to develop applications, and in Google’s latest application release, it used one. CNet confirmed today that Google (NSDQ: GOOG) used an undocumented API in order to add a nifty feature, which allows the phone to sense that you want to conduct a verbal search, rather than using the touchscreen. The reason that developers shouldn’t use the APIs is fairly legitimate — Apple won’t ensure that these features will work when it upgrades its software. CNet said Google may be forced to rewrite the code for Google Mobile or change the way the application uses the proximity sensor if Apple decides to enforce the terms of the SDK. However, the bigger concern is that Apple doesn’t have the manpower to scour the applications as well as it needs to. The same bottleneck is found with the carriers, which can take months to approve and roll out an application. To Apple’s credit, it’s been churning out hundreds, if not thousands of applications a month, but the problem may become even more of a burden in the future. The obvious way of dealing with this is becoming more open, so it will be interesting to see if Apple increasingly bends the rules in an effort to keep up with the fast pace.