I noticed if you log into your Google account (which has Gmail, Drive, etc.) then you are also logged into your entire Apple (in my case iPAD Pro 10.5) device.
I am not sure how this works, but if it is that way then this is a serious/huge mistake.
Here's the thing: I was using the Google Drive iOS app because it had passcode/Touch/FaceID internal protection, so I could look into a few private files such as IDs scanned, family photos, etc. from a specific GOOGLE account.
Let's say the account was branaghan@gmail.com.
So by logging into the Drive app there was no need to do this again, files were available 24/7.
Then I had an idea: to use another account in Documents by Readdle, another app.
readdle.com
It can also access Google stuff.
To my surprise I saw
branaghan@gmail.com
Listed there. Then I proceeded and the app just asked my permission to grant authorization to view the files. It was logged already!
No need to input any password.
This is beyond absurd. If this were working properly we would need to log into each new app manually! And insert all passwords each time.
*********
I also noticed a different Google account I am using for the Youtube app:
Is also listed in the DRIVE app as available to be accessed.
******
Then I checked what was going on with my Google account, and saw this:
The iPAD was listed there. if I hit "log out" then all apps will stop accessing such account.
Is that Google's idea of security?
I am not sure how this works, but if it is that way then this is a serious/huge mistake.
Here's the thing: I was using the Google Drive iOS app because it had passcode/Touch/FaceID internal protection, so I could look into a few private files such as IDs scanned, family photos, etc. from a specific GOOGLE account.
Let's say the account was branaghan@gmail.com.
So by logging into the Drive app there was no need to do this again, files were available 24/7.

Google Drive
Google Drive, part of Google Workspace, lets you securely store, intelligently organize and collaborate on files and folders from anywhere, on any device. With Drive, you can: • Safely store and access your files anywhere • Edit and store 100+ file types, including PDFs, Office files, videos...
apps.apple.com
Then I had an idea: to use another account in Documents by Readdle, another app.

Documents by Readdle
Documents is a home for all your files. Watch movies, listen to music, open ZIP files, download MP3 on iPhone and iPad.
It can also access Google stuff.
To my surprise I saw
branaghan@gmail.com
Listed there. Then I proceeded and the app just asked my permission to grant authorization to view the files. It was logged already!
No need to input any password.
This is beyond absurd. If this were working properly we would need to log into each new app manually! And insert all passwords each time.
*********
I also noticed a different Google account I am using for the Youtube app:

YouTube
Instale o app YouTube oficial em iPhones e iPads. Veja o que as pessoas ao redor do mundo mais gostam de assistir: desde vídeos de música famosos até conteúdo em alta sobre games, beleza, moda, notícias, aprendizado e muito mais. Acompanhe canais que você curte, crie seu próprio conteúdo...
apps.apple.com
Is also listed in the DRIVE app as available to be accessed.
******
Then I checked what was going on with my Google account, and saw this:
See devices with account access - Google Account Help
You can see computers, phones, and other devices where you are or were signed in to your Google Account recently. You can check google.com/devices to make sure no one else has signed in
support.google.com
The iPAD was listed there. if I hit "log out" then all apps will stop accessing such account.
Is that Google's idea of security?