I had this happen a lifetime ago back when I was a teen still. I think it’s not that unusual to have this happen when you are young and new to dating. I wasn’t totally sure it was an official date and neither were they, so they brought a friend along. We all had a fun time hanging out!
I think this reads as something someone new to the dating world would do. I think it felt natural because the nature of if it was even a date wasn’t something concrete. If we both were showing up with stronger romantic intentions it might have felt unnatural, but we were acquaintances already and this was more of a vibe check at the time.
While neither of us were interested in pursuing things romantically, we did remain friends. Not that intentional romantic pursuit was even on the mind really.