Pugh wore a black dress with a turtle neck.
This is very common in her line of work anyways, Being a model.
In the second one, Florence Pugh is pulling her undergarments off over her head, then turning her back to a guy as we get a wider view that shows her butt again.
Her performance in the latter film won her the British Independent Film Award for Best Actress.
We see her nude ass.
Her ass is just the exact type needed to fit into her model-figured body.