These preformed panel kits are ok. They do the important job of accommodating the differential movement between the shower tray and the abutting joint down onto the tray sides. This has always been the weak spot for shower trays. If the tray is not solid and is not bedded properly then it moves when stepped into. This then distorts the joint between the tray and wall tiles. Even silicon sometimes will not make up for a poorly installed shower tray. They have there place these panels and are easily installed or removed or replaced.

Cheers Concrete