What Mr.Sharma does not seem to get is Apple is very particular about user privacy. In the past users have been tricked into giving out their private data or scammed into subscribing to really expensive subscriptions by scammy apps (http://thehackernews.com/2017/06/apple-subscription-scam.htm...)
I am not saying TRAI's app is going to scam users but Apple's concern is genuine. TRAI can work around it by changing the away the app collects the spam call data from a user's phone. They certainly don't need the entire call history.
Here's where things get odd. TRAI has a tough job on its hands too. They cannot simply allow users to report any phone numbers as spam callers without verifying it. The reason is simple. It opens up the possibility of misuse via fraudulent reports. Those who have dealt with the Indian market will recall that fraud is rampant in the system - both by users as well as businesses.