create method in Rspec
It looks like create is called from FactoryBot.
Usually you need to create object like FactoryBot.create(:user) but if you configure factory bot
RSpec.configure do |config| config.include FactoryBot::Syntax::Methodsend(see this) you can omit FactoryBot and use short variant create(:user).
So your code creates factory practice with creator which is created by another factory physician.