Most Youtubers used mud mortar instead of thin-set mortar to create the initial curb. I am wondering if my contractor's practice will work

Isn't the shower door supported by hinges attached to the wall?

The PVC is the waterproofing.

@Mark Bischak, Architect Thanks for the reply. I thought the curb also needs to carry the weight of the door so it has to be solid/hard enough.

Wood curbs always crack. Wood curbs with fasteners through them on top rot too. I do not find a wood curb acceptable.

@User What material would you recommend building a curb with? Thanks!