"Arranged as a members-only union, the new organization won’t seek collective bargaining rights to negotiate a new contract with the company. Instead, the Alphabet Workers Union will only represent employees who voluntarily join, as reported by the New York Times. That structure will also allow it to represent all employees who seek to participate — including temps, vendors, and contractors (known internally as TVCs) who would be excluded by labor law from conventional collective bargaining."
That sounds to me awfully like a voluntary union, though I'm not familiar with the laws allowing unions in various US states to compel non-members to join.
That's not to say I don't like like the idea, which I prefer to traditional Unions where participation is forced.
I believe that's incorrect. IIRC, the contracts apply the specific classes of workers at specific locations.
I have a friend who works in HR and I know for a fact that their company has different locations that do similar work: some are nonunion, some are union, and the union locations do not all have the same union.
Union contracts with the company typically bar the company from keeping or entering contracts with non-union workers that have different terms from those of the union.
In many (23) US states, when a union forms at a workplace, it can compel all non-union workers to pay fees to the union, weather they want to join or not.
I think most US workers would be for unions if they were presented as you described, where you can choose between different options or working without a union.