Thank you so much for posting this!
I suppose the term "trans widow" is objected to by transactivists on the basis of our ex-spouses' supposedly being "the same person inside." But to us, a spouse who rejects his maleness, and especially those who transition and go on to insist they never be referred to again by their "dead name," is as good as dead, even if we choose not to identity ourselves by that term "trans widow."
I completely understand (and share) your desire not to be defined by your STBX's choices and neuroses; I can also understand why using the term "trans widow" would feel like a capitulation to that.