It didn't, so called CC province was actually pashtun majority region.
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It was not even proper province like SIndh/Punjab. Pakistan made Balochistan a province, gave them identity and a capital which was not theirs. A parliament.
Lasbela a sindhi speaking region could easily have been merged with Sindh but no, the idea was to appease the baloch at the cost of others. There is no question of legitimacy as Pakistan/India wouldn't have allowed little independent countries all around them. So not sure why you want referendum now.