Why are transgender prayer requests "too far"?

Many theologians have said that transgender people shouldn't pray that God would change their sex because God doesn't make mistakes. But, every petitionary prayer is based on the premise that you know better than God (e.g. you're poor, you judged that God didn't give you enough money in your life, so you ask for more; someone is an unbeliever, you judged that God made a poor decision in His divine election, so you pray that he or she be converted). Why does praying that your sex would be changes constitute going "too far"?