People say this about all sorts of things that have caused them horrible suffering. It's not specific to trans people at all. e.g. Jorge Luis Borges wrote after progressively turning blind in his 30s and 40s that:

A writer, or any man, must believe that whatever happens to him is an instrument, everything has been given for an end. This is even stronger in the case of the artist. Everything that happens, including humiliations, embarrassments, misfortunes, all has been given like clay, like material for one’s art. One must accept it. . . If a blind man thinks this way, he is saved. Blindness is a gift. I have exhausted you with the gifts it has given me. It gave me Anglo-Saxon, it gave me some Scandinavian, it gave me a knowledge of a medieval literature I didn’t know, it gave me the writing of various books, good or bad, but which justified the moment in which they were written.

Is this just a coping mechanism? Basically yes, but there's nothing wrong with that. If someone feels better about themselves because of it then I'm happy for them. But it's also totally fine to hate the bad things that have happened to you and to be angry. Personally, I feel both the two emotions at different times.