"Said" being the operative word. Talk is just talk. I predict that if any union-forming attempt is made, Bowser's opinion will change with frame perfect accuracy and this statement will be memory holed. (Although unionization of Nintendo employees is unlikely to happen in Japan anyway. If it does, it will more probably be within their American or European subsidiaries.)

We should remember that Nintendo is a privately held, for-profit company run by Japanese people. They have their own ethic, the company belongs to them, and profit comes first. They might make video games and franchises we like, but they are not good guys. There is tons of well documented past behavior on their part that illustrates this in many ways.