That is not true. Apple can still require you to provide access to certain areas such as contacts and photos. Apple would need to fortify the side loading mechanisms. When the app is loaded, it behaves like a normal Apple app, except it just hasn’t been certified by Apple
Of course its true since all he app needs to is ask the user for such access to contacts etc. The user allows the app to break out of the sandbox, ergo the app is not 100% isolated. Also apps have access to stuff without asking users such as clipboard and messaging with other apps.
That is not what I mean by malicious. Malicious here means someone who is creating an app that prioritizes being a bad actor, e.g sharing data to the dark web. Many millions are not creating apps like this.
First I consider collecting data to show target ads a malicious act.
Also, Apple stopped 150 000 app submission in 2020 for violating privacy policy. 1+ milion apps rejected for objectionable or illegal content, 100 000+ rejected for misuse or unnecessary use of personal information. 500 000+ developers' accounts terminated for distributing illegal content.
So yes, there are millions of them being malicious.