ya most often its just tagged to a really well grown strain... But there all actual platinum strains... Like a platinum og that is a OG x Aghani. There is a strain of just 'platinum' a homie has been growing for nearly 10 years, and its just a nice kush like indica. Like a master kushy/bubba kush plant... WHen he says platinum, people are like "platinum kush?" and he replies, "No, JUST platinum".
but in the case of cookies and cherry pie, the term platinum just means really well grown, or the real deal.. The 'platinum' cherry pie, is no different than regular cherry pie. As for cherry pie, the 'mutant' pheno is the durban leaning one, and the 'normal' growing cherry pie is what is being referred to as the 'gdp leaning' CP.
And ya, the GSC does have a lot of vigor. But almost any strain ive grown from seed/taken clones off has that same amount of vigor. You figure the GSC was probably sprouted from seed less than 5 years ago, so its still relatively young and vigorous... Although im sure there are cuts out there that have been through hell with broad mites/ revegges, and have lost some of its vigor.
Personally, i think Cherry Pie x OG should have produced something far tastier/superior to the GSC. The GSC is definitely some kill, but the taste/smell wasnt what i expected. And i think the cherry pie is a much yummier smelling strain