Yes, it is effectively security by obscurity using the fact that nobody knows exactly which compiler options you tweaked, but the reality is it works really well since almost all exploits need to know some code offsets very precisely to work.

Also, many state security agencies have a ready to go exploit for the latest iOS, but they don't have a team ready to assemble a custom exploit for your modded android.

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Make sure you get down to the comment by ardbiesheuvel, “linear map randomization was already broken”, past all the hot air about the lack of QA. This comment explains why hot pluggable memory causes issues with randomization.

Now off to read the article.