Yea, the word choices could be better. Assuming you can only have a MAX of 2 workers, there's an example or worker usage which contradicts the assumption. Thus, I reinterpret the rule as, "If you have no workers, then take 2 workers, otherwise, take 1 worker."
You can have more than 2 workers, but you can't get there by way of Action 4.
Choosing Action 4 when you already have 2 workers is pointless and will not you get above 2 workers.
(In fact, one might even interpret the rule as saying that, if you choose Action 4 with 3 workers, you drop down to 2.)
You can get more than 2 workers by playing knowledge cards to your estate