I arrived in TPE at 11pm on Thursday and the CDC were already at the gate. We were separated into non-Taiwanese and Taiwanese lines. If you wanted to leave the gate area you needed to complete and sign the quarantine form. So for an ex-TPE run (which I have done numerous times before), I think there are a few potential scenarios - 1. Denied boarding in HK per post above; 2. You get sent quarantined (assuming you are a HKSAR passport holder); 3. You refuse quarantine and get sent back on the next flight to HKG; 4. You get a personal escort to your connecting flight.

I have no idea which is more likely. It was an extremely chaotic situation. But for sure I agree that if you are non-HKSAR passport then 1 is the most likely scenario.

As for health checks, you only had to complete health declaration and do a fever scan, nothing else.