Phenotype is an organism’s appearance as determined by genes and genetic responses to environment. Chopping off a penis and artificially growing breasts does not change a person’s phenotype because the changes were not driven by genotype. He is still physiologically and genetically male, which means a lifetime of medical treatment to maintain the illusion of switching sex. His gender may be considered to be “woman” if society really wants to complicate matters, but a male is a male and a female is a female by very consistent scientific standards that are as rigid as the code written into every single one of our cells. Until that code can be uniformly and permanently altered after conception, this is the science. Everything else is fantasy.