I am downloading XCode 10.3 now, will see if it resolves the false positives on iOS 12.2 & 12.3 for Obj-C. In the meantime I was lucky enough to have a device with iOS 12.1.2 running that I could leak check my code on ( XCode 10.2.1 + IOS 12.1.2 is not showing the same framework leaks / false positives ). So if you have a device running an older version of iOS 12.1.2 that might be a way to differentiate the false positives from real leaks. Will update once I run some tests on XCode 10.3 + iOS 12.x. Fingers crossed.
**Update** Just ran a few quick tests: 1) iOS 12.3.1 + Xcode 10.3 still shows numerous leaks in various core frameworks. 2) iOS 12.1.2 + Xcode 10.3 running exact same code shows no framework leaks. 3) There seems to be an iOS12.4 update available, next step is to try combo of XCode 10.3 + iOS 12.4 and see if the problems is eliminated. Will update when I get a chance to give it a try.
**Update** XCode 10.3 + iOS 12.4 resolves the issue for OBJ-C Metal & AVAudioEngine application in my testing.