Вот список настоящих UNIX™

    Apple Inc.: macOS version 11.0 Big Sur on Apple silicon-based Mac computers
    Apple Inc.: macOS version 11.0 Big Sur on Intel-based Mac computers
    IBM Corporation: AIX version 7, at 7.2 TL5 (or later) on systems using CHRP system architecture with POWER™ processors
    IBM Corporation: AIX version 7, at either 7.1 TL5 (or later) or 7.2 TL2 (or later) on systems using CHRP system architecture with POWER™ processors
    Cemprus LLC: DNCP Series running FTX Release 3  
    Hewlett Packard Enterprise: HP-UX 11i V3 Release B.11.31 or later on HP Integrity Servers
    Hewlett Packard Enterprise: HP-UX 11i V3 Release B.11.31 or later on HP 9000 Servers with Precision Architecture
    Huawei Technology Co., Ltd: Huawei EulerOS 2.0 on Huawei KunLun Mission Critical Server
    IBM Corporation: AIX 6 Operating System V6.1.2 with SP1 or later on Systems using CHRP system architecture with POWER™ processors and 2, 8 or 128 port async cards
    IBM Corporation: AIX 5L for POWER V5.3 dated 7-2006 or later on Systems using CHRP system architecture with POWER™processors
    IBM Corporation: z/OS V2R1 or later with: z/OS V2R1 or later Security Server and z/OS V2R1 or later C/C++ Compiler on IBM zSeries Processors that support z/OS Version 2 Release 1 or later
    The SCO Group, Inc.: UnixWare ® 7.1.3 and later for single and multiprocessor systems based on IA-32 and compatible processors and conforming to PC architecture
    The SCO Group, Inc.: SCO OpenServer Release 5 and OpenServer Release 6 on Single and Multi-processor Industry Standard Intel architecture platforms

Один дистрибутив GNU/Linux я в нем вижу, а FreeBSD или OpenIndiana в упор не вижу.
Этот список это единственное что определяет UNIX™ перед нами или нет.
Не фантазии виндузятников с опеннета, а список по адресу https://www.opengroup.org/openbrand/register/