It's not meaningless, but NiN's success may not simply be determined by how many Switch units they sell. They could sell 75 million and it may not matter overall. This is because of the Switch's hybrid design.
It's totally possible that based on these record breaking Switch sales so far, that this has/will lead to some, if not many of their handheld customers becoming hybrid customers instead.
If NiN ends up with 75 million Switch customers, but "loses" 50 million handheld customers because they bought into the hybrid concept, well then NiN isn't really that much better off. They may make more money overall do to having one main type of hardware and software, but that still doesn't make Switch itself a massive success. Sure it may look that way at 75 million sales, but that won't be the truth behind the scenes.
It wouldn't be much different than taking any PS customers and having them all buy a PS4 or having PC users who play XB games all buying a XB1. The sales of those consoles would be much higher, but the user base wouldn't be any larger and PS/XB income wouldn't be all that much higher either.
Holiday 2017 Switch sales will be the main indicator of how well the system will continue to sell going forward. If it can take its place amongst the PS4, Pro, XB1S, Scorpio, then its future is bright. If it fails to secure a position, then its future is bleak.
PS1 - ! - We must build a console that can alert our enemies.
PS2 - @- We must build a console that offers online living room gaming.
PS3 - #- We must build a console that’s powerful, social, costs and does everything.
PS4 - $- We must build a console that’s affordable, charges for services, and pumps out exclusives.
PRO -%-We must build a console that's VR ready, checkerboard upscales, and sells but a fraction of the money printer.
PS5 - ^ -We must build a console that’s a generational cross product, with RT lighting, and price hiking.
PRO -&- We must build a console that Super Res upscales and continues the cost increases.
