Unions literally cannot guarantee you money, dude. Other than what's in their coffers, and what is "drawn up" in advance, collected for, and spelled out in a written agreement.

Especially fragile new unions, they don't have jack shit going for them. The company isn't going to help it form, and they might choose to fire dissenters attempting to unionize. During a strike or demonstrations, even with a formed union, the company isn't going to pay the workers for not working. In this way, the company is correct in saying "there are no guarantees of pay". Hell if they don't like you there's no guarantee of a job at all, if there's no established union.

It's all talk, speculation until a formed union draws up a legal, enforceable contract that both company & union agree to. CBA, as it's called (Collective Bargaining Agreement).