Surprised this hasn't gotten any attention yet. This issue also affects me. It completely broke packaging yet again for Rarity. You guys really need to test with multi-line keys any time you touch the localization portion of the packager.
When you include via .pkgmeta a library which has been localized with curse, packager uses the localization data from the including addon EVEN for the library, so localizing via curse a library is right now impossible.
I am afraid that packager is very very low in their priority, even if addon writers are their main asset (as the reward program prove)