I can tell you what it most likely is.
As mentioned in the description they have used the original Skywalker OG clone to create this strain and if you think about it there is only one option that makes sense:
It has to be:
Skywalker OG clone x OG#18
Of course there is no other way to bring a clone to seed and what makes more sense than hitting it with the OG#18.
And the other would be to reverse the Skywalker clone itself...and releasing that. Instead of releasing Sky18 which is a new strain entirely. Pisses me off that they even named it Skywalker....It isn't the SkywalkerOG I know and love AT ALL. Granted I got 1 keeper out of 1 6-pack of beans, which is pretty good, but, if it had been a selfed skywalker, I might actually end up with a pheno that IS the Skywalker. My 6 beans were all different phenos, NONE OF THEM WERE Skywalker. Had one I called Vader...That was a keeper. Potent as shit, tasted like awesome feels....all that, still would'nt call it Skywalker.
"The blueberry x mazar that Dutch passion stock, I do believe, is a completely different strain, simply given the same name. The Skywalker we use was an OG Kush phenotype grown out for its high yields which has been a big hit in California so we stabilized it in seed form by crossing it with our already stable OG Kush, bringing about, the Skywalker Kush, great OG Kush taste, if not better, big yielding like the Skywalker, if not bigger!" -DNA
It's not stable at all. "...by crossing it with our already stable OG Kush." When they did this, crossing the clone with the OG18 fem pollen, they created feminized F1's, that means every single plant's gonna be different, and some will be utter shit. I had 1 utter POS in my 6 pack. 2 OK's, 1 ehhhh I'll smoke it, and 2 keepers (by looks, taste left me with 1 keeper.) By no means is Reserva Privada's "Skywalker Kush" a stable strain. Delving in further I can tell you 2 were sativa-dom, 2 were indica-dom, 1 was 50/50 mix and 1 was a 12+ week pure sativa. That's about all I can say about it...You might find some great stuff, but you might not. It's a crapshoot like everything else.