Will the Shadowline crack on Intrim Shadowline Skirting?

No, it won’t so long as you follow the correct installation instructions.

During installation we recommend using Fiba Fuze tape which creates a strong, seamless join, without the risk of crack appearing. To avoid cracking you must also allow the jointing compound to dry fully between coats as per the manufacturer’s specifications and instructions. Drying times are approximately 24 hours in normal conditions or 48 hours in cool conditions between each coat. See USG Boral instructions here.

You can see in our demonstration video that even a sledgehammer cannot break the join.