Finally, a subject I'm very familiar with. I'm an American Filipina, cook and bake many traditional meals and desserts.
As with any dish, ask 10 people their recipe for, i.e. apple pie and you will get 10 different recipes, maybe similiar, maybe vastly different, but different from each other more than likely.
So with Bibingka, different Filipinos have their own version. Most recipes use sweet rice flour (Mochiko is a popular brand) and some use rice flour for a more "cakey" bibingka. Some use more eggs for a more "eggy" custard like texture. Hopefully, you have access to Asian food stores who carry frozen grated cassava. My recipe for Cassava Bibingka differs slightly from your linked recipe, if interested I'll post mine. Good luck and hope you report your results!