I cant say if it’s because of the sex stigma in the usa or because it’s just weird

Context could make it better I guess - like maybe the sons a sex/porn addict or something along those lines.

But you said this particular context makes it worse (and the only worse context I can think of right now is she had it molded to herself) so I would have to say it’s pretty abnormal.

my mom bought me playboys back in the day somewhere around my 14th/15th birthday and I was pretty weirded out by that relatively ‘benign’ act.