Probably just 10% of it's copies were sold through bundles based on the total number of bundled software sold in each fiscal year provided by Nintendo.

Top 100 Nintendo published games
Updated Software as of 31st March 2023, Switch games colored purple

I think the original MK8 on WiiU actually has the higher attach rate. It sold 8M+ on a system that only sold 13M. It may have had some holiday bundles here and there, but so did MK8 Deluxe, and I don't think bundles were a majority of the sales for either game.

TOTK's opening brings the Switch to 19 games that have sold over 10 million, (soon 20 when Switch Sports cross the line, it probably already has) and once it inevitably reaches 20 million, 8 games over that number. (9 when Super Mario Party cross the threshold soon)

For comparison, their highest selling system ever, the DS, has 10 games over 10 million and 3 over 20 million.

Where is new Donkey Kong ? ;(

No, 19 10mil sellers, not 16. And the DS has 3 over 20mil.

Ah, typo. The 15 in the OP plus Tears, Diamond/Pearl, Splatoon 2, Pokemon Let's Go.

VGC estimates have Brain Age overtracked apparently. 

The Wii has the highest number of 20+ million sellers besides Switch, at 7 games, so tied with Switch. Either Mario Party or Tears will break that tie soon.

You should never take any software estimates made here on VGChartz seriously in any way. So ridiculously many of them were completely wrong beyond belief.

Official numbers is all you should use:

https://www.nintendo.co.jp/ir/en/finance/software/ds.html

And Wikipedia has pretty solid lists all with good sources, mostly Nintendo reports for best selling games on various consoles. Here for DS and Switch for example:

https://en.m.wikipedia.org/wiki/List_of_best-selling_Nintendo_DS_video_games

https://en.m.wikipedia.org/wiki/List_of_best-selling_Nintendo_Switch_video_games

Finally, the unfamous quickrick cliff

Clearly the entire time he was just talking about that so he was actually a genius.