Interesting!
My first reaction is to shout a resounding "Yes! They have transitioned because they said they did!".
But then again...
The whole meaning behind the word "transition" (generally speaking) is to go from one thing to another thing.
One could argue then, that transition is purely an act of the (somewhat) physical, social and legal. All external things. Our "core identity" doesn't change. We know who we are before we undertake such an important monumental task.... if we've thought things through, anyway

.
So - if someone did not change those outward things - did they "transition"? Would one classify accepting, acting on, or discovering something that is already pre-existing as "transition"?
Hmm... it's a sticky one!
We all have different paths, and no path is "better than" another path. There's only the best path for an individual, and it's up to them to create it (etc, etc).
Personally, I do think they've made some kind of journey. I'm more inclined to think of it as a journey of self discovery, at the end of which they've found a way to express themselves and be comfortable in who they are without resorting to an external "transition".
And if someone only changes a "few" things? Well, they've gone through a smaller transition with different start and end points.
There's nothing inheranty wrong with either of those things.
The mistake I think people are making is comparing different transitions side-by-side and trying to create some sort of classification or order out of the chaos. We start doing that, then we're going to start putting people in boxes. We do that, then we're going to start stacking boxes on top of each other, and someone is going to get crushed on the bottom.
As for me, I will consider myself "fully transitioned" when I no longer feel like making, or am not planning (even unrealistic plans are plans) any more sex related changes. I have no idea when that could be or what it entails. I'm just going to keep doing things until I don't want to do - at which point I'll stop.