That’s true - this ember CLI change doesn’t impact the HTML or CSS parts of themes/components.
In general, you can identify problem theme components by looking for yellow deprecation notices in the browser JS console under the old non-ember-cli environment. (Moving to Ember CLI is the reason we’ve been introducing these deprecations)
Meta has been running Ember CLI for a number of weeks now, and we’ve been working to make sure all our official themes/plugins are working in the new environment.