Jon realized he was more shaken up by the whole thing than he had thought. He was not, after all, female from the waist down. Being female from the waist down was a side effect of the genitals wish and not something he asked for, so he was able to reverse it. He had wished for his clothes to fit him and the stone had reshaped his body to fit them. He had also changed his voice back to what it had been yesterday. So except for his vagina, he had a normal boy's lower half and a normal voice, not a female lower half or a feminine voice.
Besides, if Jon had really had a female lower half, he wouldn't have needed to show Jeff anything, since it would have been obvious.
"Do you guys, um, like, are you gay?" asked Jeff.
Which was a troubling question. Even having just a vagina and no other female parts would still have changed things. For all he knew, maybe in this new history he was attracted to guys and did date them after all.
The best way to answer that question, of course, was to use the stone. He reached into the shorts pocket where he had carefully put the stone, touched it, and said "I wish that first, nobody else notices this wish, and second, I knew exactly how my history is different in this new reality now that I have a vagina."
As the answer came to him, he realized at least he knew the answer to Jeff's question....