I think for many years the seats in CE and ET are the same seat. They move the curtain forward/back according to demand and in the older planes pull a lever to adjust the width of the seats (shrinking the B seat and making D/E/F all a bit wider). But it's the same seat before and after the curtain. Otherwise how could they handle moving the curtain? Carry the seats in/out several times a day?

I've never been on any BA A320 where the CE seats are different to the ET ones behind the curtain.