But the person replying isn't saying that Caitlyn ought to be referred to by her former name. In fact, they aren't actually using it to refer to her at all. They're merely mentioning that it exists, which is appropriate in some contexts.

If I were going over medical records with my doctor, she would be fine to ask if (deadname) was my name, because it's for a necessary purpose. That's different from using it to refer to me.

Also, if Caitlyn is offended by seeing that name, she's going to have an awfully rude awakening coming under the current administration. I think the time for subtlety is past on that front.