I would say that this is not normal and is a common practice in other airlines
In July I flew Cathay Pacific NRT-HKG-BKK, the NRT-HKG was in eco and HKG-BKK is in bus.
And on the NRT-HKG leg they have some pork with rice for economy and then later on the HKG-BKK they have the same pork with rice (same wording on menu too) for the Business.
So it's not only TG. It's also CX.