so no one could self a clone and produce seeds of the pheno?
Not only "can" this be done, it HAS been done.
There are several breeders who have jumped on the bandwagon, and are selling what they claim are S1 offspring of GSC right now.
The problem is, contrary to what they (and internet "experts") would have you believe, S1 ceeds are NOT genetically identical to the self-crossed parent.
An S1 cross is a sexual cross, just like any other, and if you cross two hybrids, you end up throwing off a lot of phenos.
In this case, GSC is such a hybrid, and the S1 ceeds should be expected to throw off a lot of different phenos. Most of these phenos should have SOME traits from the parent, but because of recessive genes and general genetic variation, many of them will have traits NOT seen in the parent.
Of course by random chance some offspring should be highly similar to the parent, but these will be more the exception than the rule, and you may have to grow out 10 packs of ceeds before you find something like that. This also presumes that you have grown the "real" GSC and would be able to recognize it, if you saw it. . .most people buying such ceeds simply would NOT be able to do that!
Think about it. If it were possible to create good ceed versions of "clone only" lines just by self-crossing them, there would be no such thing as a "clone only" line.
Bottom line, nobody has "real" GSC in ceed form and whether or not its even possible to create something in ceed form that's a consistently good approximation of the famous parent is questionable.
If you want the real deal, you have to get your hands on a clone.
Alternatively, there are also a number of new strains out there using GSC as one parent. Again, while these may well be great in their own right, obviously GSC x "something else" isn't going to be the same as GSC.