Exactly. This is a lot like when people pick out a still-frame capture and talk about how bad it looks as a transfer... when it might just be that one frame.
Picking a single frame and saying it looks better in widescreen is of little real value. Also, someone else pointed out that the "missing info" that we don't see in 4:3 is usually seen a frame or three later as the still-frame is part of a panning shot that shows it all anyway... so that goes out the window too.
All this single-frame = proof stuff has gotten out of hand in various places on the internet if you ask me. We aren't evaluating still photography, so we really shouldn't be looking at single frames out of context.