It's just that its so.. minor. If you ever wanted to implement this in your app then there are multiple ready-made solutions for this or you could write your own in a short amount of time. Presenting this as one of the key new features in a major new OS versions seems just strange.. like there wasn't anything else substantial.
Measuring glyphs, dealing with reflow, kerning, whitespace breaking rules, etc is no fun
They develop for a certain size and resolution, maybe what is currently on the Samsung flagship, and if it also work outside of that box they are happy. And if not they simply flag it as not supported in the Play store.
Android has had from day one all manner of capabilities for fitting a UI to different devices. But still i run into UIs that seems fixed in some manner because of some Photoshop designer with a chip on their shoulder.
I think you are attributing malice to something where laziness would be an easier explanation. As an occasional Android dev, I know the laziness problem all too well when trying to get UI to fit multiple devices.