This doesn't have the same uncomfortable context as the korean spa scene in Big Mouth. An undeveloped toddler quickly running through a store with her pants down doesn't have any sexual or pedophilic undertones, it's just thrown in there as a gag because kids find butts funny.
Big Mouth constantly sexualizes the children characters who are going through puberty and brings up sexual topics, the spa scene focuses on tweens and older women's uncensored nudity for over a minute while trying to convince you that it's normal for young girls to get naked with older women and girls who are still not through developing should be comfortable enough with their bodies to be okay with getting treated like an adult and sexualized.
Kids should not be getting sexualized by the show's writers or the audience. If they wanted to do a body positivity message they could have done it in another way.