But when the user taps on the login button the app authenticates with one of the already added google accounts without prompting the password.
That's why is called One Tap sign-in, so you can sign in with a single tap. Using this approach, you don't have to choose the same account when signing in, as it's already known from the previous sign-in.
If you have already implemented Firebase authentication with Google, in order to be able to choose another account, then you have to revoke the access from Google as well as from Firebase. Because you tagged as a programming language Kotlin, then I recommend you read the following article:
And here is the corresponding repo. If you'll see some differences, between the article and the repo, that would be because I constantly update the project to the latest dependencies and add new fixes and improvements.