I agree. There was a time when workstation meant a computer used for technical/business stuff, and a PC was a "toy". And during those times workstations were Sun, HP, DEC, etc. I remember using HP-UX machines with "unheard" amounts of RAM (128MB), while a typical PC was still playing games with Expanded vs Extended memory in DOS, typically 4 or 8MB maximum RAM. Linux was not a thing yet. PC's could run Windows 3, but "real" work which needed a Unix workstation meant, Sun, HP, IBM or DEC.
The Sparc/UltraSparc was a very good processor (and so was PA-RISC and the DEC Alpha) and supported 64-bit long before x86 did, but eventually the evolution of the larger x86 PC market grew to where x86 CPUs caught up to, and then outperformed the workstations of old, and made custom RISC processor development costly and irrelevant.
As all the RISC CPUs migrated to IA-64, and then got beat by x86-64, there was also the movement away from the different Unices (HP-UX, Solaris, VMS, etc.) to Linux. It was the combination of x86-64 performance and cost improvements coupled with the explosion of Linux on PC hardware that made the old Workstation model obsolete (SPARC/Solaris, PA-RISC/HP-UX --> x86_64/Linux).