Pretty sure they are still using quadrature positioning. The back of the motor has a segmented doughnut magnet on it and nearby halleffect transistors sense the moving magnetic fields to determine how many revolutions the motor makes which equates to how far the shade has moved.

There is some error in this process and it can start to pile up over time.

The left shades travel gets "shorted" while the right shade "lengthens". This can lead to a very noticeable difference between bottom bar heights.

Battery voltage will affect speed of movement. One shade reaches position before the other.

Also the shades are not synchronized when coming out of sleep mode so one shade can start to move before the other shade has received th command.

Periodically moving the shades to their home position "all the way up" will help to minimize "creep" caused by the magnetic encoding.