You dont have to "buy it" Joe90, but it is true. How widespread is the other question. And do you want to risk it in your T-GDi. My 2.0T hasn't missed a beat when using Quaker State but I'd rather not continue the beta test and just use lower Ca oils from here on out.
Even the high Ca user SOPUS has admitted as much but tempered their warning by suggesting it's only an issue in prototype engines. Not true as there's been a few (known) market released examples where LSPI has been the cause of breakdowns and failures. Chevron Ornite has also moved away from high Ca formulations as evidenced in the most current PQIA test samples.
Chevron Ornite
https://www.oronite.com/products/lspi.asp
The Role of the Lubricant in LSPI
"Many factors have been demonstrated to impact LSPI, including: engine designs, fuel composition, and lubricant composition. On the lubricant side, the most noticeable impact has been from the detergent chemistry. Oils with higher concentrations of calcium, which is found in many detergent systems, have been shown to increase the frequency of LSPI."
Pennzoil
Pennzoil's Q & A, the topic came up again and they have answered it this way. Remember, SOPUS oils are rather laden with CaSa...
http://www.bobistheoilguy.com/forums/ubbthreads.php/topics/3836844/Pennzoil_Answers-Complete_Prot
Q: Could you address operators of GDI-Turbo vehicles regarding the effects of certain additives such as calcium and their impact on LSPI (low speed pre-ignition)? There's much discussion and concern by operators of these vehicles that Pennzoil's additive packages are predisposed to LSPI as compared to other brands.
A: Low speed pre-ignition (LSPI) is more a phenomenon of engine design – and as you mentioned, occurs more frequently in gasoline direct injection (GDI) turbocharged engines. It is really a phenomenon for prototype or experimental engines that are still in the Research & Development phase, and oils with high levels of calcium-based detergents can increase LSPI frequency. HOWEVER, by the time the engine is fully designed and released to the market, it must be compatible with the available motor oils in the marketplace. Thus said, there is no need for concern.