I don't know enough about this particular instance, but if it was true, my opinion of it wouldn't be much different than the usual types of DLC. I've played other games where content that was typically present was suddenly locked away, and it annoyed me in those cases too.
In recent memory, Tales of Xillia comes to mind (not recently I guess, but I just beat it last year). Past games generally had a collection of costumes you could unlock for completing miscellaneous sidequests. Xillia had a few, and offered little accessories to make up for it, but more the most part costumes were sold as DLC. It's something I found annoying, but just put up with at the time. I always liked having an assortment of costumes to show off my in-game achievements while going through multiple playthroughs, so having them locked away behind a paywall was a disappointment to me.
So I guess it's not something I'll defend...but I wouldn't lambast Nintendo for it either, as there are plenty of similar examples out there. Personally, I like having the physical figure more than just a digital ticket. I only have two amiibos, one of which was bundled with a game, but so far I haven't really felt like I'm missing out on anything for not purchasing certain figures, or have gained much extra with the figures I have. Just a neat bonus...so far.
NNID: Zephyr25 / PSN: Zephyr--25 / Switch: SW-4450-3680-7334
