A doctor here said fresh ejaculation from masturbation on toilet seat could cause a pregnancy, is this true ( does vulva ever touch seat)?

That would take some: real doing !! The ejaculate would actually have to make it to the introitus (opening of the vagina) or into the vagina. Thus, casually sitting on a toilet seat would not do the trick. I would expect that most women's vulva do not touch the toilet seat - that would be pretty gross.

Less likely: No she literally has to scoop the sperm with a syringe and put inside her genitals. Though such stories have been told in contested paternal cases but I really doubt the likely hood