I can answer from previous experience using the TWOVTransit Without Visa (TWOV) in Beijing and Guangzhou: I had each time two different tickets, on different reservations (going to PEK/CAN with CX, leaving with KE or OZ).
I printed out both tickets and showed that both in HKG (so that CX staff would let me fly) and at Immigration in the Mainland. The unexpected plus was that there was a special line for TWOV, with fewer people.
I haven't done a TWOV since Covid (I got myself a Chinese visa ASAP), so can't confirm this is still the case.