Probably because they were forced to memorize times tables, but not arithmetic so they wanted to show where they are leveraging that memorization from

The post is poorly written satire that tries to imply that neurodivergent people discover different methods of solving problems, and doing so angers neurotypical people who, being neurotypical, insist that neurodivergent people are wrong for doing so.

In reality, it’s a tumblr post that, while not entirely inaccurate, is nevertheless quite divorced from reality.