So many people mistake the two. Some were even whining on the wiki.
It doesn't help that the game decided to treat people mistaking the two artists as each other as an in-game gag by giving Heroine X a black sword and a white sword for her Noble Phantasm and having her dual-wield them, ala Kirito's two most well-known swords (though it could also be a shout-out to EMIYA with Kanshou and Byakuya given Heroine X is trying to kill her past self).