Replying to ktiedt:
I guess we are unclear what i18n path we are getting taken down then -- how do you ensure you get "non legacy i18n"?
My explanation at comment 3, though accurate, was somewhat incomplete/misleading. The bottom line is that the builder automatically converts legacy bundles to AMD. So if you delete localized files from the output and then try to load any of the deleted locales, the program will fail to load. That is normal, correct behavior.
Again, if you want to output a build with fewer locales than are in the source root, then the solution is to delete those locales from that source root. To my knowledge this was not a legacy option. It is currently not an option with the new builder and doesn't seem that generally useful. The problem could be easily solved by writing a custom transform to go before the writeAmd transform. Of course that's a fairly advanced option and we don't have good docs on how to do that yet. Please confirm this is your issue and I'll try to help out with that transform.
As mentioned in comment 3, none of this applies to flattened bundles. For those, you will get exactly what you ask for with localeList...no more, no less.