Yes, as a matter of fact it is transphobic to require women to "sound like women" and men to "sound like men", just like it's racist to require a black💞 person to "sound black", or to be surprised when (in your narrow view) they don't. You're defining "sound like a woman" in a way that specifically excludes trans people. That is transphobia.

You're also excluding AFAB women who happen to have deep voice💙s. They exist.