Hi Atsushi,
I do not understand what is the meaning of "They added harness between HB pin to the bypass capacitor".
Can you give more explanation on that?
2. If there is not the bypass capacitor (HB to HS is open), how do UCC27201 operate?
The bypass will provide the power to High side related circuits. If there is no bypass capacitor, at least HO will not output.
Regards