If the voice actor doesn't change into a male one later, I don't know what to think of it anymore. Since the vast majority of anime use (adult) female voice actors to voice underage boys, it's nothing peculiar if he sounds like a girl here. Few anime use child actors in the first place, and those shows tend not to be action shows or anything like that.
Most shounen/seinen isekai have a male MC, most shoujo/josei female. That's just how it goes. Since isekai series in general are exceedingly escapist in nature, it makes perfect sense. Of course there are also some exceptions, but, surprise surprise, they tend to be... you guessed it, gender bender/homosexual.