How are the Catholic church's teaching on plastic surgery and GRS self-consistent?

GRS (gender reassignment surgery) is the term given to procedures (several usually being required) which change the appearance of an individual from one sex to the other. My understanding of Catholic church teaching is that it is broadly in line with this post where it appears that the reason is that this form of appearance altering surgery is classified as "despising [one's] bodily life". As gender reassignment (surgery, hormone replacement therapy etc.) is considered a therapeutic treatment for gender dysphoria I take it that it would be considered a "therapeutic medical reason " for sterilisation (where that is necessary in GRS), to say nothing of permissibility of gender reassignment for individuals who are already sterile (some intersex individuals, post-menopausal women etc.) So it appears that the reasoning for this is that it is considered hateful to your bodily life. However, it seems that plastic surgery which is also an artificial way of altering one's appearance is permissible even when not being done for therapeutic reasons? While the same post states that gender reassignment surgery is not permissible? Indeed it is described as "inherently immoral" - is this because it is indicative of hating your bodily life or is there some other reason, of which I am unaware, which makes gender reassignment surgery inherently immoral? What is the Catholic church's way of explaining this apparent inconsistency?