Jim ..... previous threads about Cedar Creek have covered this "Shad" question. As far as the "most logical" reason ... seeing as how there are several other species in Cedar Creek, that were not 'stocked' -- it would seem most likely that the KDFWR did not kill out ALL of the resident species (as planned), and Gizzard Shad were not completely eliminated.
It has been alluded to (rumored) that some landowners, of the upper reaches of the creeks, did not want the creeks (running thru their land) poisoned (livestock, crops affected ??? ). But, that's just speculation ... only KDFWR/those landowners would know for sure.

And yes .... the Gizzard Shad would be detrimental to the sunfish population/size ... for the simple reason that Bass prefer the soft rayed Shad, over the spiny rayed panfish, for a food source. This would allow/account for the stunted size of the sunfish population, because the sunfish population would not be controlled by the predation from the Bass.

MY biggest concern, is why the ban on Shad is still in effect ?? They're already established in the lake, so why not let castnetters help thin out the population ? The only "reason" I can come up with, is that it may cut down on the purchase of minnows (from the local venues). But that's just MHO.

"Stirring the pot" is easy, when it comes to Cedar Creek !! ...cp