No, it's a very good reason as to why they did not add that to the game.
"Good" isn't the word for it. It is a reason why they did it, but not a good one.
"The game was originally targeted for a Japanese only audience"
Last I checked there were gay people in Japan.
"there was no outcry for any changes because no one thought it was needed as a feature."
There were, however, a lot of people happy about finding the glitch and buying the game because of it, and disappointment when it was patched.
It is getting bent out of shape and serious over nothing because it's just some goofy unrealistic, cartoonish, family, and kid-friendly game that obviously is meant to be light hearted and and not to be taken seriously.
I'm not seeing how any of that justifies excluding homosexuals from the game.
"By the way, I just so happen to be autistic and I'm appalled by the fact that autistic people won't be depicted in this game either."
It really shouldn't need to be stated how stupid of a strawman this is, but obviously your own player avatar represents an autistic person because you're the one playing it. This isn't remotely the same as a homosexual making a player avatar that is then forced to be outwardly straight.