Looked at another way, Tracey is the star of the show and has to be in the sketch - if she's uncomfortable with the nudity then she gets the special effects treatment.
The Daily Mail reports that despite Pippa receiving an injunction banning any publication of the photos, she knows how these things go.
Also Tracey's is a consistent colour without variegation; Pippa's changes subtly across her torso as a real body does, including what looks like a swimsuit neckline tan.
Well, maybe I'm going blind , but I agree with J-Sth.