My recollection is also that local notifications didn't exist yet in 2010 on iOS, or had just been added. I tried to confirm it but it's actually pretty hard to find that information, it seems. Could be wrong. But, I was heavy in mobile and push notifications just after 2010, so I'm fairly sure that's right. I distinctly remember that as a feature that was added, at some point.

I've been able to set a repeating alarm forever

It's entirely possible the app author made a poor choice. We have no control over their code. All we could do is try to deliver our meager little component as competently as possible.