story time,
Rio had major complex about his singing for a long time and has talked about it in various interviews even off-stream with his genmates/senpai. At some point he's not even sure if people wouldn't be put off by his voice characteristic but decided to push through and got surprised with how quickly his watchers grew to like his singing.
If you're also familiar with the seiyuu scene, they have people like Aoi Shouta or Murase Ayumu who could pull off "feminine" voice effortlessly yet are 100% male confirmed.
Small opinion but I think it's easier to identify someone's trooness by the way they acted so there's that