What's happening, if Japanese Castella sponge cake with RICE FLOUR.

It is an incredibly soft and amazingly delicious Castella easy to make.
ingredients
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5 Large eggs (250g) - at room temperature
Half a cup of sugar (120ml, 100g)
1/3 cup of cooking oil (80ml, 75g)
1/3 cup of warm milk (80ml, 80g)
A pinch of salt
1 cup of rice flour (240ml, 120g)
20cm x 20cm square pan
150 degrees (300 F) convection (fan-forced) for 60 minutes