That's one of the reasons, Iwata said so ages ago iirc.
But... Have you seen the quality of materials in Zelda and Xenoblade games? If it wasn't for texture resolution, they'd look just as good as any other modern day game.
When you work your textures on Substance Painter (standard texturing software), you don't save time, money nor any other resources by making the assets at smaller resolution, the results have infinite resolution due to the nature of its internal functioning and that can't be changed no matter if it's for next Kirby game or for RDR3, that's just the way it works.
If anything, you'd probably be using more resources because the assets have to be manually downscaled depending on your production pipeline and tools.
Also, creating stylized assets isn't inherently cheaper or easier, or even less demanding on hardware.
Using Substance again as an example, you'd actually have to be very good and spend extra time in order to make non-realistic textures on it since "realistic" is the default easier way to produce them.
Zelda BOTW and TOTK don't make less calculations in their lighting tha your average AAA game either, they actually do way more than any 7th gen game and are more comparable to 8th gen games due to using full PBR pipeline, realtime lighting at big scale and manage many variables for temperature, reflections, specularity level, etc. just for materials to be shown properly.
Same for Xenoblade, the difference between Xenoblade X and Xenoblade 2, save for resolution, are like half or full generation apart due to lighting and materials alone. Xenoblade X used same old PS360 graphic pipeline while Xenoblade 2 used full PBR pipeline which is more akin PS4/Xbone.
Their games are probably cheaper to make not because of the hardware though, they are because they don't waste time making horses balls shrink on cold and instead prefer the cold to actually affect the gameplay or just not do it at all. They don't bloat their games, they go straight to the point and work on the actual meaningful stuff.
They're the epithome of "less is more" in a very functional and effective way.