Not necessarily. Economic development can be limited to the owners of the companies whilst exploiting the employees. That is what gave rise to unionization, it was a reaction to abusive practices.
That unions later on became self sustaining and that they work against the interest of some of the people that are employed (seniority system for instance) has nothing to do with why they exist in the first place.
This is often heard but there is little truth to it. The more developed a market is, the larger the opportunities for employees to move to other jobs, and therefore exploitation is a problem that goes away by itself. Many countries in South East Asia have close to zero unions yet benefit from very high living standards and reasonable working hours (at least very much equivalent to the US).
If the "union" theory had any truth in it, then you would expect unions to be everywhere in the world before and during economic development to lead social conditions improvement. Yet social/working conditions improve regardless of unions presence.
You can't take something that works in Switzerland out of that context and then apply it to some other country with the arguement 'it works in Switzerland'.