Who even uses that definition outside of super niche communities?

So a good person who behaves like Christ but grows up in a rural village and has never heard of Christianity or read the Bible would be a Christian under this definition?

And literally literally means literal except in the vast majority of its usage.

Along the same vein, the majority of Christians are not followers of Christ.

Nah, he was Jewish, he had to be to fulfill the Jewish scriptures he claimed proved he was god. He literally called himself the King of the Jews. Even according to Christians, people didn't invent Christianity until after his zombie corpse died again.

Like, Buddha couldn't have been Buddhist, we based Buddhism on him.

Also, if 99% of the members of a group agree on what membership means, it's the 1% that disagree who aren't really members. Maybe consider changing what you call yourself if it's at odds with 99% of the people calling themselves that.

Looks like a guy you would have on a bowling team.

Most scholarship I’ve read doesn’t seem to think the historical Jesus was presenting himself as the Son of God.

For me it makes sense when you think about philosophers and psychology schools. Lacan didn't considered himself lacanian, but freudian. To almost quote himself "people ask me if I am lacanian, that I leave that for my followers. I consider myself freudian". It is a dynamic of who you followed built their own material with other people material, so having a not christian Christ is not the same as having Christ not believing in himself, but considering the path he went through to build his teachings.