No, it's a stupid notion.
They would only benefit from supply manipulation, if they have incredibly high profit margins. Or if they are in control of their market, a market leader or monopoly.
Also, people should keep in mind Nintendo is a public company with shareholders to please. And they judge Nintendo's performance quarterly. I don't know if Nintendo said anything about supply to shareholders, but Nintendo can't purposely lie about their business to shareholders. If they say they have supply issues, it is mostly true, unless if they wanna risk getting sued.