The Philippines does not allow for dual citizenship and having it is basically worthless. Not worth giving up any citizenship for it and even if you could have dual citizenship, it doesn't really offer you anything worth having - only partially useful if you wanted to own land here but there's ways around that too.

As former citizenship holders they do have some rights (mainly when it comes to getting processed at the airport) and I think if they want their citizenship back it's not that hard to get but as mentioned there's not really a good reason for it. As a foreigner it's pretty easy to get into and stay in the country, even for extended periods of time.