No, the assumption is that companies are more interested in cutting labor costs than productivity. Even if you screw up and need to hire back 50% of those you fired, you still cut the labor costs of the 50% still fired. And you can pretend to be a cool, thought-leading, "AI-native" company, which might be enough to juice your share price enough to offset any actual productivity loss.

Capital will always be in opposition to the cost of labor and want to make it as close to zero as possible, and AI is a plausible story for attempting that, regardless of the reality of AI efficiency.

No the assumption behind the statement and many others on this topic is not AI is more productive than Human + AI, it’s that 9 (or 8 or 6) humans + AI is more productive than 10 humans. No one is suggesting getting rid of all workers, but many are saying they can get rid of a significant percentage of them. It remains to be seen if that ends up being true but it is fundamentally different from what you are describing