As others have mentioned there are apps in the wild that do this. I use a notes app Notion.so which does auth like this.
To be honest I didn't/don't like it because it's an extra step and I use a password manager anyway that makes it easy to fill in my passwords.
As I'm reflecting on it though, it's not that big of deal as I use the mobile and desktop apps which I'm signed into all the time. I would imagine if it were an app I had to log into again all the time or frequently I would be pretty annoyed with it.
To be honest I didn't/don't like it because it's an extra step and I use a password manager anyway that makes it easy to fill in my passwords.
As I'm reflecting on it though, it's not that big of deal as I use the mobile and desktop apps which I'm signed into all the time. I would imagine if it were an app I had to log into again all the time or frequently I would be pretty annoyed with it.