Both this and the WaPo article are extremely light on the details what exactly these employees said or did. WaPo says that these employees "violated company policy", which leads me to believe they must have been saying something that Amazon felt was untrue, because again, official policy is that you can speak as much as you want about working conditions at Amazon as long as they are factual. I would like to see what exactly these people said that apparently upset Amazon, but I can't find it anywhere.
factual: Amazon does this factual thing X and this factual thing Y, and it shouldn't be happening this way.
First one is just an opinion piece, regardless of its truthfulness, because it cannot be evaluated objectively (how to objectively determine whether amazon cares or not? who counts as "amazon" in this scenario? what factual event led to this statement? and on and on).
Second one is a factual statement that can be evaluated on a true/false basis. Events X and Y either happened or they didn't. If they did, the responsibility for those can be traced and evaluated. It leads to actual results, while the former is just an emotional opinion sort of statement, but that's exactly what sells the headlines.