Yes it is and is more visible than standard cornices. If there is some movement in your foundations or frame it can be more noticeable with square set.

What causes cracks in cornices?

Cracking cornices and plaster cracks are a common feature that often occur naturally in a new home. Ground movement and natural settling can occur with minor cracks appearing in walls or cornices, often several years after the house has been completed.

Is Square set cornice more expensive?

Square set is more difficult for the plasterer and is definitely more expensive than most cornice options.