You'll notice how great the spheres look and how unpleasant the mech looks...

so then I said, well maybe it is just flat surfaces..

Oddly it isn't lower resolution as much as it looks like flat surfaces have a zoomed in appearance. Now you could say, well is it your shader. NOPE. I tested in several other games.
Why didn't you notice until now? Truthfully, we didn't make that much of a usage of just reflection. Specular always obscured it when reflection was really high, so was specular.
so I created a new test unit to look at it

all images are clickable to larger versions
is there a way to tell spring, hey I WANT a higher resolution reflection cubemap to be generated? maybe that can mitigate this issue?