The --l10nsrc and --locales options cannot be used independently. You must either include both options on the command line or exclude both options from the command line.
The two options are applied uniformly to all model files on the command line. If you want to compile two (or more) models that have a different list of locales or with different l10nsrc base directories, then you need to use two (or more) different dynmodel calls.
When dynmodel generates Resource Packages, it will incorporate files for each model based on<dir>/<pkg_id> (where <pkgId> is the model file name less its extension, plus "_mm", then truncated at 23 characters.
In this example, dynmodel compiles two models, model1 and model2. The dynmodel compiler incorporates ./mysource/model1_mm/ja.txt and ./mysource/model1_mm/de.txt into model1’s .dat file. The dynmodel compiler also incorporates ./mysource/model2_mm/ja.txt and ./mysource/model2_mm/de.txt into model2's .dat file.
dynmodel model1 model2 --l10nsrc=mysource --locales=ja,de
If you do not include the --l10nsrc and --locales options then dynmodel will not look for any localization .txt files, and the .dat file for the model will only support the native language of the .mdl file.