Just 3 rows of CE for TXL would be very small, albeit this flight operates mid afternoon (scone and cream time!) away from peak time. I am not clear when this flight is scheduled, but typically you would expect it nearer 6 to 8 rows in the final analysis. But the reason for these moves is that the CE curtain will move in and out to allow some seat selection without allowing people to scatter themselves over a big empty cabin, which then causes problem if ET sales require them to bring the curtain forward. Seat shifting in CE isn't unknown by any means, but it's fairly rare on the whole. The main potential victims are the ET passengers close to the front of their cabin, though there is normally a 4 to 6 row buffer left unfilled to minimise ET issues.