Being transgender isn’t about who you are attracted to, it’s about who you are. Just like a woman can be attracted to another woman and still be a woman, or a man can be attracted to other men and still be a man, a TG is still TG if they are attracted to other TGs.
Like you, though, I do find it interesting that a majority of TGs seem to be attracted to other TGs (I’ve found that to be the case in many groups where this issue was discussed, not just here). I’m solely attracted to straight men, so I don’t fall under that group, but I do wonder if there is some reason for that preponderance of TGs preferring other TGs sexually. I’m just curious. I am a cultural anthropologist so these issues interest me.