You might want to actually read what the article says in it and not the title .
They were talking about how after they released the DLC for Breath of the Wild which got a gameplay reveal at the game awards 2017.
they wanted to add more but they couldn't because DLC is just adding more data to a preexisting title.
But the ideas they had for a sequel required more than what was possible with DLC.
Nothing in that article backs up what you say.
I can see your argument about Elden rings DLC being counted a a stand alone game, I'm not gonna argue against that as I don't really care.
But ears of the Kingdom literally uses a different engine that Breth of the Wild:
And Nintendo Switch Sports!
gonintendo.com
Hence why when Tears of the Kingdom came out so many devs shared their surprise :
IGN spoke with five game developers — ranging from indie devs working on their first solo projects to devs with decades of AAA experience — about the most mind-blowing parts of Tears of the Kingdom, and if a universally-loved game like this is inspiring, deflating… Or a little bit of both.
www.ign.com
Also just remember the creator of Elden Ring claims those previous Zelda games you are calling DLC should never be compared to his games as his games are unworthy of being compared to Zelda:
Hidetaka Miyazaki, the creator of Dark Souls, took part in an interview with Rolling Stone. At one point, Rolling stone says “many journalists over the years have said that the Souls games, from Demon’…
mynintendonews.com