Neckband fold

Hi, I am working right now on the neckband in a 1x1 rib on a James C Brett jumper pattern for a 1 year old. The pattern is chunky and mainly in st st.

The pattern suggests that I have to knit 14 rows in 1x1 rib for the neckband and fold. I have been told by someone that I could just do 7 1x1 rib rows and cast off.

Can I do that? How will it be different? Thx

You can certainly work the rib for the length you would like and then cast off. While the turned under neckband is very pretty, in chunky yarn on a baby it might be too thick and uncomfortable.
Be sure to cast off loosely, perhaps with a size larger needle in your right hand to make sure the cast off isn’t tight.