No, this is asking for special treatment 100%. I treat literally all people with a facade to keep them away. Literally nobody can make me address them in any special way.
There’s nothing special about addressing someone as “her”, that’s just normal every day communication.
And how do you determine if it’s true?
Someone created a Cis or Trans Quiz with 25 pictures: https://uquiz.com/quiz/ACfqeR
My Results: https://uquiz.com/Result/static/lite/ACfqeR/4866525/scored/68?&s=4adba41d-150b-4d50-9b6f-93817a24ca47
It takes less than 5 minutes, feel free to link your perfect score (Note how only 78 people scored higher than 90%). Otherwise your only options to determine if it’s “true” would be insisting on seeing their genitals, making you a sex offender, or to take them at their word.