Yep, also Grizzly Research is a short seller, and this lawsuit was filed by an Arkansas attorney general. Arkansas makes really bad decisions like weakening child labor protection laws, don't trust anything that comes out of that state.
If this report is true, it would reflect poorly on Apple and Google more than Temu.
iOS does have protections in place that prevent an App from modifying its own executable code; the current argument about Emulators in the EU is showing that Apple is very strict when it comes to this sort of thing.
Even if the App was able to reconfigure itself to access data it does not have permission to access, it still needs to ask for permission.
I assume Google have similar protections in Android.