@ngx-translate and the update of the www/i18n/*.json files

I’ve installed @ngx-translate to have my App translated in two languages (it & en).
The translation files are in “src/assets/i18n/it.json” and “src/assets/i18n/en.json”.
I’ve seen that running “ionic run build” and "ionic serve -lcs" to test the app the files in the www/i18n/ directory is not updated.
I’ve to update by hand these two files: "www/assets/i18n/it.json" and"www/assets/i18n/en.json".

Is it normal or am I doing something wrong?