A UI/UX designer wrote the code.

Now I’m not saying coding is rocket science (because it isn't), but there are certain types of people who are a little (too?) obsessed with thinking of ways their logic can break and covering it with checks and tests… I'm guessing that designers are less likely to be one of those.

I love designers, btw. I think UI/UX is a hugely underrated discipline (see: "dark patterns", designing for safety). But unless you stare at logic all day, the implications of a code change like this might not immediately strike you as a risk.