I have confirmed internally that:
What you’re seeing can come from two different permission layers.
If the user is a super admin and was using work access mode, then being able to remove/delete the project would be expected, even if their role on that specific project appears as Viewer.
If they were not using work access mode, I’d next check the project’s own permissions. Projects can also have project admins, and project admins have full control over the project. It’s also worth reviewing the project’s Review project permissions and privacy settings to confirm whether the user had broader project-level control than expected.
@Irish_Makimura thank you very much. As I can see work access mode is available only in Enterprise and Enterprise+. I’m on Advanced plan and I’m superadmin. My client is on Asana Advanced too but he is not superadmin. We both observe the issue without work access mode.