Looking how he does because of the influence of the belief of humans gives them an idea of what he is, more or less. Meanwhile, Flowey couldn't care less if his reaping was indiscriminate, it was a turn of phrase.

"By the way I should mention this place likes to bring… uh, copies of the same people," Frisk says. "Actually "alternate" is a better word… like, two people but with different experiences, possibly from a different time or world."