Well, some people do, as they think the Switch is the WiiU-successor. I think the japanese understand it is already the 3DS-successor.

It's also worth pointing out that the Wii U was launched during the holidays, which the Switch was not. This does matter. Some people made a big deal about the PS4's sales in its first couple of months in Japan lagging behind the Wii U's, conveniently forgetting the PS4 was a February launch. Sales data shows that systems that launch during the holidays obtain a clear benefit from the Christmas shopping season to their sales in those early weeks of their lives, whereas systems that launched outside the holiday have no such benefit. The Wii U actually had the best third-week sales of any home console released in Japan in the past 20 years, and even if you count handhelds released since 2000 it was only beaten by the DS and GBA in third-week sales. It's second-week sales ranked #2 among home consoles released in the past 20 years, beaten only by the PS2, and even then only by 25.6%, and that's after the PS2 having launch week sales over twice that of the Wii U. Meanwhile, the PS4 found its baseline very quickly because there was no Christmas holiday in its early weeks to help boost sales. It exhibited a clear "hockey stick" curve, which we also saw with the 3DS.

Basically, it's pointless to compare LTD sales for these first few weeks. What really matters is baseline sales, and we should have an idea of what the Switch's 2017 baseline will be by the end of April.

You forgot perhaps the most important thing. A lot more games (3rd party) released here than anywhere else. So with more stuff to buy/play there's going to be less people buying the Switch for Zelda.