the thing is, even if there were an OPTION for akira to be bi, if the player didn't want him to be, he wouldn't have to be. they could play him perfectly straight and decide their akira was straight. similarly for if someone headcanoned him as gay. giving the player more options doesn't restrict the protag's possible image, that's just kind of silly.
MY THOUGHTS EXACTLY!!!!!!!!!!!!!
the question isn’t “why make him bi” it’s “why not”???? because like you said, if you open up the option for gay romance you can just ignore it entirely and boom, your akira is straight. or you can pursue it full throttle and he’s gay. or you can dip your toes into each and he’s bi. esp if generally speaking in more RP-leaning games the protag is supposed to be more of a blank slate than the rest of the characters, like in fallout where you can choose dialogue options that make you a total dick.
apparently it would go against the “clear personality” akira has and like… i’d argue that his personality def leans towards bi? you can literally flirt with all of the male characters at some point so idk how that was a contending point for boyf lol (i said as much and he was like “i would say ‘honey i’m home’ to a dude and it wouldn’t be flirting” and i was like “cool but for someone else it might be which is the beauty of having a bi character”)