Spouse Visa Extension - Sole Responsibility

Hi, we are in the process of completing the application for a spouse visa extension, covering my wife and her two children (all Philippines nationals). When we applied for the initial spouse visa, we included quite a lot of documentation (e.g. school, medical, other care confirmations/bills etc.) to prove she had sole responsibility for the children. In the extension application, it seems all that is now required to evidence her sole responsibility is a birth certificate (states this at the end in "other documents" to be provided).

Is this correct i.e. we just provide birth certificates for the kids this time around rather than a more extensive set of documents ? Makes sense given the kids are already here and we have provided the necasary evidence first time around.

Any guidance very much appreciated. Thanks.