AlanB,
That is exactly why I believe the term "emergers" is too broadly applied.
The imitations with trailing shucks have reached the surface, but have become "stuck " and offer the trout a great opportunity for feeding.
As another example, Craig Matthews and Jon Juracek's tremendous pattern the "Sparkle Dun" is often referred to as an "emerger". The beauty of this very effective pattern is that it represents a crippled dun, stuck in its shuck, and easy prey for the trout as it can't fly off......