Fab house will use the board cutout data directly from the gerber file along with board outline and
use it to route the slot.
If you need it to be PLTD, add copper on both side along the cutout and point it on the fab dwg it to be PLTD.
I've seen FAB shops miss board outline features in the Gerber files. That's why I want to get the data into the NC files.
Callout will definitely help.