The parent term is "Collective action problem", but, like calling all nasal tissue paper "Kleenex", people often forget the parent term and use the most well-known specific term (including me, recently).
Okay, so because the Blizzard employees aren't unionized, they can't force Blizzard management to back off this plan. I get that, and if those workers decided to unionize to address this issue I think that would work. But it doesn't stop them from seeking employment at other remote work companies. If the collective of employees at Blizzard can't or won't unionize, seeking employment at other companies is their next best option for those individual employees who care the most. That 'commons' hasn't been ruined, because such remote work companies really do exist and are a realistic non-ruined option.
"The commons", here, is the status quo of the last couple of years in which many employees at all software companies could work remotely. This commons is now being sectioned off into companies that allow full use of this resource, and those who don't.
This is a tragedy, and it is a tragedy about a common good that briefly existed as a common good, but it's not technically a "tragedy of the commons" in the original sense.
I understand people conflating the terms in this example.