I believe this is the reason, the GTL based oil performance is pretty similar with PAO, cleans better and cheaper. I think European producer has put this formulation for years even for long drain BMW spec driven in autobahn
GTL doesn't clean any better than PAO, the beauty of GTL is that it comes even closer than traditional group III in many of the performance metrics where group III approaches PAO, such as oxidation resistance, and it also has better cold temperature performance than traditional Group III's, but still not as good as PAO (as it's still a waxy base, unlike PAO).
However, the more severely hydrocracked a base is, the more "dry" it is. Ergo, GTL also has solvency that approaches PAO, and Group III already wasn't much better than PAO in that department, so ultimately you are pairing them with something that improves solvency. This can be a splash of ester, AN, or even lower group bases. The one thing GTL has going for it (as does Group III) is that it doesn't have the seal shrink tendency that PAO has, so you don't have to use AN's or esters to counter it. So, if you are blending something that's price sensitive, this can really help, as not only do you get to skip the expensive PAO, but you also get to skip the expensive POE and AN's, you can just use some lower group carrier base for solvency. Now, that doesn't preclude one from using AN's or say POE in making the product better, but when we are talking price point...