Transit visa applicable for indirect flights out?

Hi,
I am British, travelling from Hong Kong to Guangzhou on Friday 17th July and i don't have a Chinese entry permit, so was hoping to use the 72 hour free transit.

My flight back to London is at 10pm on Saturday 18th July with Cathay, however the flight is indirect and has 1 stop via Hong Kong. I wont be exiting Hong Kong airport and so wont be travelling through immigration as its a connecting flight.

will this still be okay to qualify for the 72 hour transit in Guangzhou? thanks in advance for your help.

best,
Tom