In all my years of interpreting, there was never brought up the interpreter's or client's sexual orientation, marital status, gender ID, etc. It's no one's business and I don't know how it would legitimately be brought up during an assignment.
It's no more "right" to demand a trans terp than it is to demand not to have a trans terp.
The only exception I can think of would be if the assignment involved a religious activity where it might be an issue. But even then, I've never heard of terps being requested by sexual category, other than male/female for sensitive medical appointments.
Normally, people make preferences for certification levels, ASL/PSE/SEE use, or specialty, such as educational, medical, legal.