Ember version requirement not enforced/documented?

[digitalcora]

After updating this addon on an old project that still used Ember 2.5, my build failed with an error about this.import being undefined. After some experimental upgrading, I determined that ember-spin-button now requires at least Ember 2.7, but this is not enforced or documented anywhere. I'm not sure if this is a bug, or an intentional change to the addon's supported Ember versions.