And then the union makes an agreement about going to the office 3 days a week instead of 5 and declares a victory for the workers.

That would indeed be a victory. Look at the status quo.

Thank you for illustrating my point perfectly.

What is the point because I guess I'm missing it. Is a union winning more work from home days for workers as opposed to not having a union and not getting those days not a win in this situation?

You have no point. You said just enough to feel indigent but literally said nothing of value. "Union bad" isn't even an argument.

It would give any employee the choice to have 2 days remote at least, which is a victory.

I'd think the majority of the factory workers would tell corporate to come to work.

Yup. Most factory workers are playing the worlds tiniest violin for all the privileged laptop class having to go back to the office.

If there are fewer cars on the road because the people who can work at home are doing so, then the commute becomes smoother for anyone who can't work from home.

Are they? I don't know any factory workers but I have friends outside of tech and they can all relate to "arbitrary rules from management that make my job harder are frustrating".

The people who spend the most time sneering at 'the laptop class' that I'm aware of are independent, ie, non-unionized, tradespeople who operate as sole proprietorships - emphatically not factory workers. The arbitrary, unproductive distinction between 'real' physical labour of the kind carpenters, roofers, drywall technicians, etc, do and 'laptop labour' is increasingly being seen as exactly that.

Then they are short-sighted, because other people WFH would be better for them too. The US culture can be staunchly individualistic and bordering on revenge-oriented, so I can't say I'm surprised.