They look like childproof outlets where you rotate them into position to use them.

See here: Safety 1st Swivel Outlet Cover, White https://www.amazon.com/dp/B000BQL7CI/ref=cm_sw_r_cp_api_i_Qr5LFbRGJG34V

I can see of some cases where this might be handy, but very unusual!

This is a 360 degree Rotating Duplex Outlet. Other than the rotating feature its a standard receptacle and still available.

I had no idea such a thing existed, that is fascinating! I can already envision installing these to help with the bulky plugs which block other outlets.

They work well with the new flat plugs.

Those actually rotate? I thought they were fixed at 45°!

I think Matt E might have the right answer. It's probably just the child lock cover. That's why it's so thick. It fits on top of the existing regular duplex receptacle.