> Finally, sadly, the most obvious point .... a longer form helps sort the wheat from the chaff. Both in terms of cutting down the volume of applications some poor soul has to trawl over, but also helping keep the quality of applications high.

Opposite effect, actually. Longer forms get you a lot of the top 10%, but you miss out on the top 0.0001% who don't want to waste their time with people who aren't smart enough to design a brief form.