its a recessed curtain niche. prior to screwing up n skimming the ceiling boards, they shouldve put timber plank/metal piece on top of the ceiling board and its metal frame for the curtain track to be screwed onto for a firm and secure hold. without that it just wont be able to last, afew pulls with the curtains or using a heavier fabric, and u will see screws losing grip on the plaster board or even the metal frames.

a pelmet is different. it is like a piece of panel, down from the overall ceiling height to cover the track. usually used to maximise low ceiling height.

u can try for an experience. btw, whats the height and width of the curtain?

seems ok, though still risky.