Nepal / Tibet / Chengdu / Kuala Lumpur Onto Australia

Hello, we are flying flying from Kathmandu to Tibet 6-16 Nov then onto Chengdu 16-18 Nov. we then depart 18 Nov for return to Australia via Kuala Lumpur. From my understanding this meets the 72 visa exemption requirement but just wanted clarity on exiting Tibet which is technically part of China. Thanks for any assistance