Has anyone tried this, not with a lens-cap or body-cap, but with ND filters? I was doing some shooting in bright sunlight yesterday, with an ND400 and f/ stop enough to get me a 30 second exposure at iso100 (to blur the water).
How about at uber-macro, like 5x mag with f/16 (which turns into f/80 or so)?
If there's enough light coming through to affect metering with the caps on, and doesn't influence much at f/2.8-5.6, there's got to be a point where there's enough to influence metering to shift by 1/3 or 2/3 stop.
Of course with the shooting I did yesterday, I was metering from live-view, and with macro I tend to either live-view or shoot-histogram-adjust. But if the metering is wrong, even through the viewfinder and only under some very specific conditions, I think it's fair enough that they should fix it...