A lot of apps (games in particular) already do this by downloading a bunch of resources on first launch. It sounds like Google is giving them a proper way to do it.

I believe the modules it refers to are executable code (dex and so files), which you're currently not allowed to download because it circumvents the app store and its approval process.

Google now supports uploading such modules to the Play store where they can be approved, analyzed and tracked, thereby allowing on-demand features without allowing third parties run arbitrary, unvetted executable code on your device.

Right... but that is a distinction without a difference: it was the case that some assets were being downloaded after the app started, and that without those assets the app did not work, and now that is still the case; the form of the asset doesn't matter as long as it prevents the app from working after the base install without first downloading whatever it is.

I hadn't seen that -- but I don't install or use most games. If I did encounter it, though, I'd probably immediately uninstall it because it would fail. I tend to keep my apps firewalled off so that they can't use the internet.

Having a proper way likely means that it will be done more often.

This is most likely only going to be used by apps that would require an internet connection to work anyways - users would shit on any dev that had something like that going on pretty quick.