Huh... we actually don't have any idea of how much time they need to make more units avaiable. Not only that, but they need to get the time rigth. If they make more that will only be avaiable 2 week after release, its a wasted effort, and retailer loss confidence in hold nintendo products. Its like the WiiU launch, when a lot of the machines remained unsold for months.
But yeah, nintendo always had a problem with distribution.
"Hardware design isn’t about making the most powerful thing you can.
Today most hardware design is left to other companies, but when you make hardware without taking into account the needs of the eventual software developers, you end up with bloated hardware full of pointless excess. From the outset one must consider design from both a hardware and software perspective."
Gunpei Yoko