Drywall screws are Philips, not Robertson. The cam-out feature is used to prevent over-penetration, which badly weakens the drywall. These bits are used; they precisely dimple the paperboard and prevent the gypsum from being crushed.

https://www.amazon.com/Magnetic-Positioning-Screwdriver-Dryw...

I do have a bunch of what look like drywall screws with Robertson heads, but I am certain that they are not intended for use with drywall.