Dumping zec as soon as you mined it doesn't make any sense to me either.
It has made sense most of the time 'cause the price keeps dropping, though there have been a couple of small spikes where it made sense to hold on to it for a short while.
I'm STILL boggled that it ever was even close to 1 Bitcoin for a price, much less the "very very EARLY adopters" pricing in the 3 digits for a very short bit.