So here's a thought... and sorry for the long post but this has been on my mind for a while.
We keep talking about how an anamorphic lens uses the entire imaging sensor and is then compressed in post. We always follow up by saying that just cropping isn't the same. But isn't it? Warning that this is looking at cropping vs. squeezing in a vacuum - I'm not talking about the other archetypical considerations of an anamorphic lens. Bokeh, flare, compression can all be achieved to a degree with the right type of filter (see: Cinemorph by Vid Atlantic), and the compression can be achieved both H+V with a wide angle adapter, so let's just talk about the cropping vs. squeezing.
Let me explain. With my camera, the 5D Mark 3, there's a fixed number of horizontal and vertical pixels which are available to be exposed. There's no in-between or random arrangement like there'd be with silver halide grains in analog film. When I record MLV at 1920 x 1080 I'm getting 2,073,600 pixels. When I record 1920 x 804 (scope) I get 1,543,680. So yes, 25.56% less pixels. But! An imaging sensor isn't a perfect pickup mechanism. It doesn't have pixels all over it. That's why it's digital - it's quantized. It's a representation, as best as possible, of an analogic wave, which turns into a stair-stepping wave when it goes through the ADC due to there being no infinite quanta (even the current standard 64 bit is "only" 18,446,744,073,709,551,616 steps).
What happens when you squeeze an image from 1920x1080 to 1920 x 804? You don't gain any resolution. In fact you may introduce aliasing due to lines being squeezed which weren't squeezed before, and the stair-stepping we're all familiar with (jaggies) comes out. Yes, we started with more pixels, and I understand the value in starting with more instead of starting with less. Analog mediums - sure - squeezing leads to resolution advantages. But digital is a fixed number of lines.
But if in the end it all has the same aspect ratio, just one didn't have any squeezing done to it (and thus no pixels deformed and/or aliased), wouldn't just cropping make sense?