There are heavy limitations on union industrial action in Australia that make this sort of thing much more likely to happen. It's a tremendously contrived system and as a result Unions often up very chummy to the employer as elements which may be more amenable to confrontation can get frustrated with the immense complexity and difficulty that brings. Any kind of industrial action used for bargaining is almost impossible to get authorized. I'd say the Australian union system is one of the worst in the world, and most Australian unions are structurally busted.

Yes, it means they cant pick you off one by one, but have to negotiate against a group that has real leverage

That assumes everyone has that option. There's likely not enough "preferable employer" jobs for everyone to have one in many sectors.

There's also a divide between tactics efficient at the individual level and that efficient at a national or global level. E.g. you can tell an individual they should be a doctor/lawyer/engineer/etc and that's good advice, but if everyone does it then who grows food and cleans floors and etc?

How do you put on pants in the morning?