I think on the contrary somewhat

If everyone at a game developer goes on strike, there is basically no amount of outsourcing or scab labour that can replace them. This is actually probably true of basically all software

Just refusing to share passwords into key systems would be enough to significantly halt any attempt to bring on an entirely new development team

Yes but what happens? The video game is not maintained or released. Society doesnt care that much. It's not critical and there are millions of alternatives.

Some historically powerful unions have enjoyed their power because their strikes not only stop their employers making money, but also impose great inconvenience on many people downstream of them.

If truckers or dockworkers go on strike there's no food on the shelves, if coal miners go on strike the lights go out, and so on.

As a consequence of this, employers are motivated to make a deal not just by missed opportunities to make money, but also by politicians, other powerful capitalists, and public opinion.

Of course there are plenty of unions where this isn't the case; theatres and hollywood are unionised despite the fact nobody freezes or starves when they go on strike.

Game developers are, I think, closer to the hollywood position than the dockworkers position.

Doing that would nuke your career. What company wants to hire someone who sabotaged their previous employer?