Yes, that's a real problem. At the same time, as long as Google is very clear why they are doing that I think they will be okay. After all, they already do this

Yes, that's a real problem. At the same time, as long as Google is very clear why they are doing that I think they will be okay. After all, they already do this on Chromebook. Now, why should they do this? Because I have seen malware sites tricking people into first enabling 3rd party apps and then installing their apk.