These are good points, but I view their efforts on ARC more as them expanding th...

These are good points, but I view their efforts on ARC more as them expanding the Chrome store's app catalog than Chrome OS completely eating Android.

And as an aside, I think many developers simply don't devote the effort to fully developing their Android apps for Chrome OS. I have an (albeit simple) Android app I publish on Chrome OS, and it's my product's most popular platform. So it gets special attention, and supports resizing with the fairly undocumented "resize" value in the app's manifest:

    "arc_metadata": {
      "resize": "reconfigure",
      "formFactor": "tablet",
      "orientation": "landscape",
    }