Why don't the HOMT tandem breakers fit into all Homeline load

Add Sub Panel in Garage two breakers in one slot As for the one receptacle that is on two single-pole breakers, it is okay as long as the breakers are installed adjacently by their length (in two slot 1-inch breakers found in residential homes are typically single-pole breakers and occupy one slot on the panel Double-pole breakers are

two slot shelving Some panels only allow one breaker per slot, while others allow slots to accept a tandem breaker, which fits two breakers in one slot