Yes, iOS still uses users in the technical "Unix" sense, they're just not mapped to actual physical users, but instead to various services.

Android is in a similar boat. They're still an important way to manage filesystem access of programs.

Android isn't in a similar boat, AOSP has full isolated Multi-User support that is realized through Unix users. You can create new users through Settings and they have their own home screen, apps and files.

Most vendors have this enabled now and things like work accounts/MDM use the same system.

https://source.android.com/docs/devices/admin/multi-user

iOS barely uses that. Processes commonly run as “mobile” or “root”, but it does not matter very much. POSIX users and access permissions are archaic, and, in my opinion, don’t match with how almost any device is being used nowadays. iOS implements its own concepts through entitlements, containers, vaults, sandboxes etc. (Look up the “Apple Platform Security Guide” for details.)

> Shared iPad security in iPadOS

> [...] User data is partitioned into separate directories, each in their own data protection domains and protected by both UNIX permissions and sandboxing.

POSIX users are quite important.

Yeah, it basically doesn't use UNIX permissions at all.

In the very early public slides announcing the iPhone, I believe Jobs referred to iOS as "Mac OS X".