Can't change individual user profile's JIRA language preferences to English if Default JIRA Language is NOT English

Some customers have accepted the limitation with English only support and are still using Studio. They ask to install a language pack (at their own risk) and we usually do this, but as a side-effect, if they set JIRA as the default language to French for example, users now can't pick English from their user profile preference page. Instead, it just shows two language options in the drop-down list, and both are French.