Existing users are registered for an application without seeing the registration form

So I have a situation with users that are in one tenant. There are two applications, A and B.

The user is registered for application A already.

Application B has self service registration enabled.

If the user tries to register for application B (they go to the registration link) they are automatically logged in.

The only way to show them the registration form is to make an attribute of the form (such as birthDate) required; then they see it.

Is this normal behavior?

Yes, if self service registration is enabled (which is set on an application by application basis) and a user who is already logged in to FusionAuth tries to register for such an application, FusionAuth will automatically register them for the app. It also checks that all required profile information is filled out, which is why adding the required field displays the registration form.