Transsexual is just the original word used for transgenders, but then it became a slur, thus the switch to transgender. Nothing to do with the operations.
"Transgender", in the original, pre-transtrender meaning, meant a person whose physical gender was the opposite (thus "trans") of their mental gender, and it applied pre- or post-op.
The new meaning, in this era of SJW redefinitions and transtrenders claiming to be trans because it's the cool thing to do and gets them social justice attention, means gender is whatever you want it to be, what you choose it to be. (Originally known as "personality" or "individuality").
For genuine transgenders, it's not a choice, they were born that way. It's a genetic aberration, and they're just trying to do their best to live with it. Claiming you can change gender at will is kind of a slap in the face to them.