Kickinbac: Have seen these flexible hoses a few times. They are used with the newish trend of baths with the integrated sides. theres no way to connect the bath drain up when installed in place with a solid pvc so it connected with the flexible hose and slide back into the final position.
If you have underfloor access those type baths are not a problem. Just drill a hole in the floor, and attach a stub of pipe to the bath outlet. Lower bath into place, then install waste trap and pipework underneath floor.
Concrete floor can still be connected without flexi pipe, as long as the customer is OK with having simple waste outlet that uses a plug. Rather than a popup type waste outlet.
edit to add
And if I have to use a flexi pipe, there is a thicker wall version available, that has a smoother inside surface.
