They're definitely not "standard Linux permissions." Yes Android does use many of those (such as standard user IDs, file system permissions, and now SELinux) to implement some of its permissions, but it adds a ton of permissions on top that are not part of Linux.
They're part of Android. Android is not Linux and Linux is not Android, anymore than a car is a wheel and a wheel is a car. Don't confuse the foundation with the building.
Here's the API reference if you'd like details [1]. They are very much not just standard Linux permissions. Android includes a huge set of APIs on top of Linux
KDE and Gnome are desktop environments that runs on top of an OS, they themselves are categorically not OS, and they don't provide OS facilitates. They don't even directly talk to RAM or core hardware without an OS managing everything in the middle.
Android is all by itself an OS, it got everything an OS should have, scheduler/trap handling, runtime, system apis/syscalls all the good stuff. It's just happened that Android currently runs on top of Linux kernel, and it utilizes the kernel to provide some aforementioned facilitates, so yes you can say Android builds On Top of Linux, but that's not saying Android Is Linux, the sentences simply mean different things.
