Never post, but I might be of use here as someone who worked as a TD in CG and VFX for many years. Yes, the kind of work being alleged here is incredibly common, and surprisingly cheap with modern tools. There is almost no Hollywood production these days untouched by an effects department, even on low-budget comedy films. From brushing out double chins or bulking up shoulders for vain actors, to completely replacing backgrounds or comping actors together due to scheduling conflicts, the amount of CG you wouldn't even notice if it were pointed out to you is crazy in today's industry.
Now, based on the shots above, I would say that yes, someone did a really sloppy job editing out at least some panties.