This also happens with CZ pre-pandemic, all of the narrowbody featuring a PE cabin will operate as a standard Y cabin and will be blocked unless they can't fill up people all in Y. I would always ask for it during check-in in CZ hubs or just go onboard and ask the flight attendant for me to switch seats to the PE cabin, the FA always doesn't mind me seating at the PE cabin, considering CZ's horrible J product on narrowbodies, and the low load factor at the PE cabin, the experience is often similar. It's like Club Europe with extra legroom(35-37 inches) with standard Y service.