Do you have the source code to Amplitude? If not, you don’t know what the binary blob you’re including in your code does.

yes, on iOS (Unity App) all of Amplitude SDK is in source code.

Yes, maybe they can't place an ad on your app but they do track all your user event data which means that they can target them somewhere else. All the iOS unique identifier, location, and user attribution data are collected directly into their servers.

yes, they collect and store that data, but what if they don't use it anywhere else other than for my app analytics?

It's a very vaguely defined rule which may create tons of additional work for developers, yet may not improve the privacy in some cases.

Well, you can always use open-source solutions in order to collect your customer event data into your data-warehouse and run your queries on your own data.