I don't know Kurt, I have seen Hydropsychids that seem to do just that on several occasions.
It's a matter of degree, Eric. The "myth" referred to is the one that assumed caddis burst from their pupal enclosures and shoot straight to the surface like a rocket with very little if any drift or swimming movement. This erroneous understanding of caddis behavior was quite common when I started out, and went largely unchallenged (at least out West) until LaFontaine. Even hydropsychids usually drift quite a bit before starting their ascent to the surface. Once there they will often drift some more before starting the eclosion process. They generally move very little during these drifting phases, as if stunned. When their hormones kick in, they eclode quickly and usually get up and away very quickly as well. As to the speed of the ascent, being good swimmers they do get to the surface efficiently with a pulsing motion, but nothing like the smooth and ridiculous speed that was assumed.
I remember 'experts' in my youth advising that you couldn't get the fly to swing up fast enough and promoted an exaggerated "Leisenring lift" with a straight downstream drift (no swing). As the fly came to the end of the drift, they recommended lifting the rod as well to further exaggerate the speed. It might work OK in gentle currents if the lift isn't too aggressive, but in the faster currents that hydropsychids seem to prefer, the fly literally ripped to the surface. I also remember it being OK at fooling little fish on occasion.:)
I no longer worry too much about trying to ape their ascension and focus on deep dead drift presentations until the fish start to show.. Then I'll move closer to the surface either with controlled swing or dead drift presentations (the latter especially with brachycentrids). Except for the occasional use of Cutter E/C type patterns, I don't seem to go with dry flies much unless I'm seeing strong evidence of floating adults being taken. It's an odds thing ...