If anything, Google's employees are in the best position to unionize. The original concept of organized labour was conceived with skilled tradesmen in mind, since they would be the hardest to replace, and therefore would have the most bargaining power. The concept of the unionized factory floor worker came much later.

From a pure leverage perspective, Google employees, especially in highly specialized areas like ML, are in an excellent position. They are legally entitled to that power, so why shouldn't they wield it?