This whole post should just be a single tweet, but somehow it doesn't feel safe to say anything comparing Android and iOS development, even implicitly, without five paragraphs full of disclaimers. First, here's the tweet:
Developers complaining about fragmentation on the Android platform are like fashion designers complaining about size fragmentation on the human body.
Expanding on that I'd say, yes, it's easier to make something that fits beautifully if you know the exact size and shape you're targeting and don't have to think about how it will look on other form factors / body shapes. Some designers create clothes for only the fashion model body shape, and some create clothes that fit a wider variety of body shapes.