Ginataang Halo-halo will thicken over time after cooking. Just add more coconut milk to thin it out, or simply enjoy its creamier texture.
Glutinous rice flour is different from regular rice flour. If you use regular rice flour, the rice balls won't be chewy. Make sure it says "glutinous". Also, "glutinous" does not mean it has gluten in it. This recipe is, in fact, is gluten-free.
When buying Saba bananas (usually available at Asian and Mexcian stores), pick the softer, mushier ones. If it's not that soft, it's not ripe yet.