Well yeah, but as "short story" is the shortest of three different groups of short fiction it is comparatively very short.

I make no claim as to the reasonableness of the problem. Perhaps people ought to be able to judge short story quality better (although I note that you are something of an expert in this field - if you weren't so good at picking winners you wouldn't keep winning awards for your anthologies). But it does happen in the Hugos and it appears to be happening in the Nebulas too.