So yeah you have no solid proof just speculation right. And yes I believe ninty is incompetent in measuring their demand supply ratios. They messed up with the Wii u but couldn't possibly determine the switch would be so popular that 2.74mil first month wouldn't be enough. Now they have to battle mobile giants for screen and memory parts so the shortage is real. As for the Wii and DS tell me which company sold 20mil+ consistently each year for four+ years? Even the ps2 legged out on a year to year basis Wii was destroying it. Hell the ps4 is selling more than the ps2 time matched but it is still very behind the Wii. Ninty is a Japanese company in the traditional sense unlike Sony and Japanese companies have always been conservative. Its in their genes not to over produce but under producing is alright. That's how they function. Ninty is also just a gaming company so if they go overboard and it doesn't work out they don't have a safety net like Microsoft or Sony. They also sell their hardware at a profit always over production would be disastrous while for Sony and Microsoft it is routine and they can just lower the price if they over produce. When you look at ninty as a business and Sony and Microsoft it's very clear why ninty always has shortages
Nintendo has actually fairly rarely had stocking problems; people way overhype things. The reality is there are certain regions that it will always be hard to stock well for compared to others. The only time I can even think of where the theory potentially has slight grounds would be the Wii era, but even then they were manufacturing LOADS of DS's at the time, so it's not hard to imagine that it was somewhat difficult for them to manufacture for home consoles and handhelds at a quick enough rate.
the fact that there is a shortage in high end parts for mobile electronics at the moment adds to the difficult in manufacturing (google if you haven't heard about the issues, the Switch uses a few of the the same high-in-demand parts that things like Apple phones also use)