Blacked-Out Profiles: Identify 26 Celebrities Behind These Shadows

My thoughts exactly.

I also thought that some of the photos they chose to use were just really awkward angles. So that didn't help.

That's not really a theory, it's more of a pretty well-known fact. Hollywood likes a particular flavor of women, like you said, "faces all conform to the same demands". We do get celebrities with unique features in every generation, very tall or short, striking eyes, or big muscles, it can be anything unique though. I had a hard time picking out most of the thirty/forty-some actresses, with every name I saw I thought, "She could be any one of them." they were all so similar.