Why is a profile.id and profile.connection_type considered only jointly unique?

[tylerkahn]

This is in the user.rb

ruby-example-applications/ruby-rails-sso-example/app/models/user.rb

Line 10 in ec5fce4

where(provider: profile.connection_type, uid: profile.id).first_or_create do |user|

Shouldn't this be
where(uid: profile.id).first_or_create do |user|