Why does the figma mask not keep the mask layer "color" or characters

I am a new transfer who uses Sketch to Figma. when I used the “mask” tool in Figma, I found it is different from Sketch.

I dk why does it cant keep colour or some “property” of the bottom layer (mask)

For example, I want to keep the Elipse colour in the mask working but I can’t keep it when I make the eclipse as the mask. it just shows the polygon colour even thought there is some area that still belongs to the eclipse. (pic 1,2) it is different with sketch.
who can tell me why and how to solve it?


it is from sketch that keeps the mask layer color