This is why we need unions. Layoffs are unfortunately, sometimes, necessary. But when they happen, it's important that the right people are chosen, for the right reasons (whether that's performance based, voluntary, protecting certain groups, ensuring fairness, etc). That requires collective bargaining by representatives who are able to assess and change the criteria, and who are able to negotiate for better outcomes…
The right reasons in a union are how long have you been part of the union. I don't support protecting certain groups. I don't agree with forcing fairness which is a personal judgement anyways. I don't even agree layoffs are necessary here. They are easy. A union doesn't stop layoffs it just costs everyone more. Your best representative in a layoff is a lawyer and a place with better employment notice pay.
GP said they can negotiate who gets laid off and what happens to those who do.
Unions can be an entirely appropriate and reasonable party.