As the application is still restricted to 50MB, and the additional space is in the form of expansion packs, this isn't likely to result in larger code. I think it is mostly to solve the consumer complaint issue.
On the other hand, no matter how ingenious you are you probably won't get a full-blown Myst or Riven on 50MB. Ever.
Which is fine if you don't want to provide that, but no barriers also provide artistic freedom. You're free not to use bloated applications.
And it's not like developers couldn't offload that bloat to be downloaded after installation.
Basically, this provides a better supported, more reliable, more standardized way to accommodate the already common idiom where many Android games will, immediately on first run, begin downloading the game assets (graphics, sounds, music, etc).