Why object_id changes after app initialization?

Rails 6.1.4.1

I'm setting values from an initializer file and when I request a page, I find the object_id of the configuration changed (and the values lost) unless I do require 'my_library' in the initializer file. I don't understand why?

app/lib/feature_flags.rb:

class FeatureFlags
  class Configuration
    include ActiveSupport::Configurable

    config_accessor(:my_key) { false }
  end

  class << self
    def configuration
      @configuration ||= Configuration.new
    end

    def configure
      yield configuration
    end

    def enabled?(feature)
      puts "#{__FILE__} FeatureFlags.configuration.object_id = #{FeatureFlags.configuration.object_id}"

      configuration[feature]
    end
  end
end

config/initializers/feature_flags.rb:

# require 'feature_flag' # If I uncomment this line, the problem is solved

puts "#{__FILE__} FeatureFlags.configuration.object_id = #{FeatureFlags.configuration.object_id}"

FeatureFlags.configure do |config|
  config.my_key = true
end

Output:

1. Run the rails server:
config/initializers/feature_flags.rb FeatureFlags.configuration.object_id = 14720

2. Request some page:
app/lib/feature_flags.rb FeatureFlags.configuration.object_id = 22880

My questions are:

• Why do I need to require 'feature_flags' in the initializer for the object_id not to change? I thought Zeitwerk was taking care of this.
• Is that how I'm supposed to do (to do it right)?

Thanks for your help!