Graphic designers work at most tech companies I've worked at, and I've never worked at a game studio. They definitely can be classified quite reasonably as tech employees.
Also, here in Montreal, most people's list of well-known local tech employers would absolutely include at least one or two of the many game studios here.
What percentage of employees at Google/Apple/Microsoft do you think are "graphic designers", and what percentage are "software developers"?
Your argument to create a union is that the 1% of employees need protection. Honestly I agree video game industries could use a union. But the presence of a graphics designer at Google does not mean every employee needs to unionize.
Google has more software developers, no doubt, but still far more graphic designers than you seem to expect.
No, every employee at Google does not need to unionize. CEO Sundar Pichai certainly doesn't. But lots of Googlers have long wanted a union for good reason, including software developers. I would have happily voted yes in a union election when I was there, despite being a software developer myself.
I know of plenty of examples of misbehaviour and other harmful actions by Google toward software development employees, a number of which have been publicly reported. And the situation seems to have gotten worse since I left.
To be clear, Google is far from unique in this regard, and it's still probably a better employer than many of its peer companies. That just underscores how severe and widespread the problem is.
Also, here in Montreal, most people's list of well-known local tech employers would absolutely include at least one or two of the many game studios here.