Afaik the "pure" G13 at least have been confirmed hacks throughout the years.
When I researched the strain, no reputable seedbank had a "pure" G13, only hacks did.
The only reputable source I could find was the MRN crosses to Skunk, Widow and Haze.
The Northern Lights seems better, there seem to be at least some reputable sources out there, including the Ortega.
I grew the Nirvana NL way back when and had nothing to compare it to or say if it was legit or not. Can only say that it was a very Indica heavy stone and seemed as advertised to me.
There might be clones of these legendary plants, including the Sweet Pink Grapefruit and others. But even in places where clones are traded more or less legally (think Austria or the recent US/CA), it seems to be very much a crapshoot if you get the real deal or just some random clone of an unknown strain that fits the profile of what people expect from a strain like G13 or Sweet Pink Grapefruit.
It is very iffy, because this whole industry has been and still is in a gray area. There is not accountability and no quality control or whatever.
And chances are that someone who bought seeds from a hack claiming to have the original G13 clone, will be heavily inclined to believe whatever he/she grew is the actual G13. Because they just spend lots of money, time and effort on growing it.
Just how the story goes... Me, personally, I decided to simply find a reputable grower and grow their seeds and make my own experiences and feel confident that I got what was advertised if the results match.
But take Bubblegum for example:
This was a top 5 strain I wanted to obtain. But there is no reputable source for it. There are people claiming to have the "real deal" Bubblegum in clone form, and I actually tend to believe them in this particular case, but obtaining a clone from overseas was not worth the risk for me. There was no reputable breeder whose seeds are confirmed as the real deal by growers out there, so I simply wrote the strain off.
I still have my eyes out for a breeder emerging with the real deal Bubblegum but neither TH Seeds feminizing their line (which already had a doubtful reputation at best before that move), nor Serious Seeds "reworking" their Bubblegum and sending out testers were anything to convince me.
Currently I believe Nirvana's Bubblicious or White Label's DoubleGum to be the best bet but I have prime genetics in my stable and don't see why I should drop down a level to Nirvana/WL...
So I wait. And I suggest to anyone who can't find a reputable breeder offering the strain they are interested in, to do the same.
I would rather sit here and wait for legalisation to proceed and more people to grow and find stuff and then hope one of them finds a "true" Bubblegum and hope by that time I have something to trade them for, than go through packs of questionable seeds in the hope of striking gold at some point.
I have better seeds to go through with a higher likelihood of striking gold