Hi,
My friend also got the same problem last month when she applied a passport for her british daughter. Yes, I am afraid it is one of their requirements now on certain circumstances.
My friend came here on fiance visa 10+ years ago/got married/gave birth in uk and now wanting to get a British passport for her daughter as it's the first time they want to fly out of uk for a holiday.
Here's what she do:
she applied online for her cenomar:
https://www.ecensus.com.ph/Default.aspx
I know it will take about 4-6weeks for you to be able to received the documents from the PH but worth a try... for you and your kids benefits.
good luck and hope it helps